A387712 Primitive terms of A387711: numbers k for which A003959(k) > 2*k, but for all whose proper divisors d|k, dA003959(d) <= 2*d.

4, 18, 27, 30, 42, 45, 50, 63, 66, 70, 78, 102, 114, 138, 174, 186, 222, 246, 258, 282, 318, 354, 366, 375, 402, 426, 438, 474, 498, 525, 534, 582, 606, 618, 625, 642, 654, 678, 686, 735, 762, 786, 822, 825, 834, 894, 906, 942, 975, 978, 1002, 1038, 1074, 1078, 1086, 1089, 1146, 1158, 1182, 1194, 1210, 1266, 1274, 1275

Offset: 1

Author

Antti Karttunen, Sep 06 2025

Keywords

• nonn
• new

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A003959, A387711, A387713.

Positions of 1's in A387715.

Cf. also A091191, A337372.

Programs

PARI

A003959(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1]++); factorback(f); };
A387715(n) = sumdiv(n,d,(A003959(d)>(2*d)));
is_A387712(n) = (1==A387715(n));

Formula

{k | A387715(k) == 1}.