A337374 Numbers k for which A003961(k) > 4*k.

16, 18, 24, 27, 32, 36, 40, 48, 54, 56, 60, 63, 64, 72, 80, 81, 84, 90, 96, 100, 104, 108, 112, 120, 126, 128, 132, 135, 140, 144, 147, 150, 152, 156, 160, 162, 168, 176, 180, 184, 189, 192, 196, 198, 200, 204, 208, 210, 216, 224, 225, 228, 234, 240, 243, 248, 250, 252, 256, 260, 264, 270, 272, 276, 280, 288, 294, 297

Offset: 1

Author

Antti Karttunen, Aug 26 2020

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• Index entries for sequences computed from indices in prime factorization

Crossrefs

Cf. A003961.

Subsequence of A337373, and of A246282.

Programs

Maple

filter:= proc(n) local F,t;
  F:= ifactors(n)[2];
  mul((nextprime(t[1])/t[1])^t[2], t=F) > 4
end proc:
select(filter, [$1..1000]); # Robert Israel, Dec 31 2023

Mathematica

filter[n_] := With[{F = FactorInteger[n]}, Product[(NextPrime[t[[1]]]/t[[1]])^t[[2]], {t, F}] > 4];
Select[Range[1000], filter] (* Jean-François Alcover, Sep 25 2024, after Robert Israel *)

PARI

A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
isA337374(n) = (A003961(n) > (4*n));