My guest blogger is David Wilson, a fellow fan of sequences. It is a nice exercise to understand how this graph works. When you do, you will discover that you can use this graph to calculate the remainders of numbers modulo 7. Back to David Wilson:

I have attached a picture of a graph.

Write down a number n. Start at the small white node at the bottom of the graph. For each digit d in n, follow d black arrows in a succession, and as you move from one digit to the next, follow 1 white arrow.

For example, if n = 325, follow 3 black arrows, then 1 white arrow, then 2 black arrows, then 1 white arrow, and finally 5 black arrows.

If you end up back at the white node, n is divisible by 7.

Nothing earth-shattering, but I was pleased that the graph was planar.

Tanya Khovanova's Math Blog

Mathematics, applications of mathematics to life in general, and my life as a mathematician.

Cecil Richards

Today Richards oversees a federation with more than 10,000 employees at 700 Planned Parenthood centers across the country. (She also helms their Action Fund.) Even in the face of deep state and federal funding cuts, the organization remains one of the largest reproductive health care providers in the nation. Abortion services constitute 3 percent of the care it provides—meaning that, yes, Planned Parenthood is where roughly 300,000 women will choose to terminate a pregnancy in any given year, often because it is the only place in their state they can do so. But those same health centers also administer more than 10 million medical services yearly—the majority to women and teenagers living in rural or medically underserved areas. That includes 4.5 million tests and treatments for sexually transmitted infections, and nearly a million screenings for breast and cervical cancer. One in every five women has visited a Planned Parenthood in her lifetime; a full 10 percent of patients are men.

How to force compiler or interpreter to see binary numbers two's complement?