A339425 Numbers k such that A001222(k)>=3 and A339423(k) divides k.

12, 36, 56, 108, 234, 260, 324, 351, 456, 476, 570, 624, 780, 855, 880, 972, 992, 1428, 1508, 1550, 2325, 2340, 2442, 2516, 2870, 2916, 3116, 3354, 3663, 3875, 4284, 4305, 4524, 5031, 5328, 6136, 6710, 6954, 7020, 7076, 7175, 7548, 7584, 7952, 8748, 9230, 9348, 9480, 10065, 10074, 10176, 10431

Offset

1,1

Comments

Terms of A339424 that are not semiprimes.

The only term in A014612 is 12.

The terms in A014613 are 36 and p*q*r*s where p<=q<=r<=s are primes and s=1+q+q*r.

Links

Robert Israel, Table of n, a(n) for n = 1..1000

Example

a(5) = 234 = 2*3*3*13 is a term because A339423(234)=2+2*3+2*3*3=26 divides 234.

Maple

R:= NULL: count:= 0:
for n from 4 while count < 100 do
  if isprime(n) then next fi;
  F:= sort(map(t -> t[1]$t[2], ifactors(n)[2]));
  if nops(F)=2 then next fi;
  T:= 0; P:= 1;
  for j from 1 to nops(F)-1 do
     P:= P*F[j];
     T:= T+P;
  od;
  if n mod T = 0 then
         R:= R, n; count:= count+1
  fi
od:
R;

Prog

(PARI) conv(n) = {my(f=factor(n), v=vector(bigomega(n)), k=1); for (i=1, #f~, for (j=1, f[i, 2], v[k] = f[i, 1]; k++; ); ); v; }
f(n) = {my(v=conv(n)); sum(k=1, #v-1, prod(j=1, k, v[j])); } \\ A339423
isok(k) = (bigomega(k) >= 3) && ((k % f(k)) == 0); \\ Michel Marcus, Dec 04 2020

Crossrefs

Cf. A001222, A001358, A014612, A014613, A339423, A339424.

Sequence in context: A039317 A298942 A322411 * A063298 A055926 A073762

Adjacent sequences: A339422 A339423 A339424 * A339426 A339427 A339428

Keyword

nonn

Author

J. M. Bergot and Robert Israel, Dec 03 2020

Status

approved