A239521 Prime powers (A025475) such that the distance to the nearest prime power is an oblong number (A002378).

25, 27, 2209, 3481, 3721, 6859, 6889, 18769, 22201, 22801, 157609, 1079521, 1630729, 1635841, 2621161, 2627641, 2825761, 3179089, 5257849, 5276209, 7447441, 7458361, 17032129, 17048641, 34304449, 34351321, 40436881, 40462321, 75290329, 75359761, 137288089, 137334961

Offset: 1

Author

Alex Ratushnyak, Mar 20 2014

Keywords

• nonn

Crossrefs

Cf. A002378, A025475, A239520 - A239523.

Programs

PARI

lista(nn) = {precp = 1; currp = 4; for (nextp=5, nn, if (is_A025475(nextp), if (currp - precp < nextp - currp, tt = currp - precp, tt = nextp - currp); if (!(tt % 2) && ispolygonal(tt/2, 3), print1(currp, ", ")); precp = currp; currp = nextp;););} \\ Michel Marcus, Apr 11 2014