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A339425 Numbers k such that A001222(k)>=3 and A339423(k) divides k. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 28 19:33 EDT 2021. Contains 346335 sequences. (Running on oeis4.)