A097106 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A097106

a(n) = (Smallest prime power >= n) - (greatest prime power <= n).

0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 2, 0, 3, 3, 0, 0, 2, 0, 4, 4, 4, 0, 2, 0, 2, 0, 2, 0, 2, 0, 0, 5, 5, 5, 5, 0, 4, 4, 4, 0, 2, 0, 4, 4, 4, 0, 2, 0, 4, 4, 4, 0, 6, 6, 6, 6, 6, 0, 2, 0, 3, 3, 0, 3, 3, 0, 4, 4, 4, 0, 2, 0, 6, 6, 6, 6, 6, 0, 2, 0, 2, 0, 6, 6, 6, 6, 6, 0, 8, 8, 8, 8, 8, 8, 8, 0, 4, 4, 4, 0, 2, 0, 4, 4

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,6

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

FORMULA

a(n) = A000015(n) - A031218(n);

a(n) = 0 iff n is a power of a prime (in A000961).

MATHEMATICA

sp[n_] := If[n == 1, 1, Module[{m = n}, While[!PrimePowerQ[m], m++]; m]];

gp[n_] := If[n == 1, 1, Module[{m = n}, While[!PrimePowerQ[m], m--]; m]];

a[n_] := sp[n] - gp[n];