A354984 Numbers that are 3 * prime powers congruent to 1 (mod 3).

12, 21, 39, 48, 57, 75, 93, 111, 129, 147, 183, 192, 201, 219, 237, 291, 309, 327, 363, 381, 417, 453, 471, 489, 507, 543, 579, 597, 633, 669, 687, 723, 768, 813, 831, 849, 867, 921, 939, 993, 1011, 1029, 1047, 1083, 1101, 1119, 1137, 1191, 1227, 1263, 1299, 1317, 1371, 1389, 1461, 1497, 1569, 1587, 1623, 1641, 1713

Offset: 1

Author

Antti Karttunen, Jun 15 2022

Keywords

• nonn

Comments

Numbers k of the form 9m+3 such that k/3 = p^k, with p a prime and k >= 1.

Crossrefs

Intersection of A017197 and 3*A246655.

Cf. A137827, A354983 (characteristic function).

Row 3 of A354930 (conjectured).

Programs

Mathematica

Select[Range[2000], Mod[#, 9] == 3 && PrimePowerQ[#/3] &] (* Amiram Eldar, Jun 15 2022 *)

PARI

A354983(n) = ((3==(n%9)) && isprimepower(n/3));
isA354984(n) = A354983(n);

Formula

a(n) = 3 * A137827(n).