A341615 Numbers k for which sigma(k) < 2k < A003961(k).

4, 8, 9, 10, 14, 15, 16, 21, 27, 32, 35, 39, 44, 45, 49, 50, 52, 57, 63, 64, 68, 69, 75, 76, 81, 91, 92, 98, 99, 105, 110, 116, 117, 124, 125, 128, 130, 135, 136, 147, 148, 152, 153, 154, 164, 165, 170, 171, 172, 175, 182, 184, 188, 189, 190, 195, 207, 212, 225, 230, 231, 232, 236, 238, 242, 243, 244, 245, 248, 250, 255, 256

Offset: 1

Author

Antti Karttunen, Feb 22 2021

Keywords

• nonn

Comments

Deficient numbers in A246282.

Not all odd terms are in A337372.

Crossrefs

Intersection of A005100 and A246282. Subsequence of A341614.

Cf. A341613 (characteristic function).

Cf. A000203, A003961, A252748, A286385, A326057, A326134, A337372.

Programs

PARI

A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
isA341615(n) = A341613(n);