[seqfan] Sister sequences

[Veikko Pohjola]

Dear seqfans,

Consider the sister sequences a1=A077065 and a2=A077068, "Semiprimes of form prime -/+ 1". Let the corresponding sequences of the cumulative sums of the terms be s1 and s2, and let d be the sequence of the differences s1(n)-s2(n):
d = 0, 0, 4, 20, 36, 52, 128, 216, 328, 464, 636, 796, 908, 1092, 1324, 1520, 1716, 1948, 2144, 2436, 2716, 2972, 3264, 3580, 3812, 4032, ...

This nice and steadily growing (so it seems) sequence is not in OEIS. Its potential general interest is in its behavior, which is difficult to anticipate by intuition. Try it! The plot of d(n) is quite surprising.

Veikko