A337543 Primitive terms of A337381: Numbers that are in A337381, but that have no proper divisor in A337381.

6, 8, 9, 14, 15, 20, 21, 35, 44, 49, 50, 52, 68, 76, 92, 110, 124, 125, 130, 148, 172, 188, 190, 212, 230, 244, 275, 286, 292, 310, 325, 338, 356, 363, 425, 429, 452, 470, 475, 494, 507, 575, 598, 627, 663, 715, 741, 759, 775, 806, 845, 847, 874, 897, 925, 969, 1001, 1023, 1058, 1075, 1083, 1131, 1173, 1175, 1183, 1209

Offset

1,1

Comments

Numbers k that are in A337381 [i.e., for which A003973(k) >= 2*A000203(k)], but none of whose proper divisors are in A337381.

It seems that 6 and 20 are the only nondeficient terms (in A023196). See also A337372 and A387708. - Antti Karttunen, Sep 07 2025

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

Formula

{k: 1==A337541(k)}.

Prog

(PARI)
A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
isA337543(n) = if(sigma(A003961(n))<2*sigma(n), 0, fordiv(n, d, if(d<n && sigma(A003961(d)) >= 2*sigma(d), return(0))); (1)); \\ edited by Antti Karttunen, Sep 07 2025

Crossrefs

Cf. A000203, A003961, A003973, A337381, A337383, A337541, A337542, A387708.

Cf. also A023196, A091191, A337372, A337479.

Sequence in context: A117096 A067812 A356312 * A047394 A184874 A085725

Adjacent sequences: A337540 A337541 A337542 * A337544 A337545 A337546

Keyword

nonn

Author

Antti Karttunen, Aug 31 2020

Status

approved