A359304 Oblong numbers which are products of five distinct primes.

4290, 4830, 6006, 11130, 12210, 13110, 16770, 23870, 27390, 33306, 34410, 34782, 37830, 44310, 49062, 56406, 60762, 64770, 66822, 70490, 71022, 74802, 82082, 84390, 95790, 101442, 103362, 104006, 109230, 119370, 125670, 127806, 133590, 137270, 148610, 151710, 158802

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

4290 = 65*66 = 2*3*5*11*13.
4830 = 69*70 = 2*3*5*7*23.
6006 = 77*78 = 2*3*7*11*13.
11130 = 105*106 = 2*3*5*7*53.

Maple

R:= NULL: count:= 0:
w:= 0:
for k from 1 while count < 50 do
  F:= ifactors(k)[2][.., 2];
  if max(F) > 1 then wp:= 6 else wp:= nops(F) fi;
  if w + wp = 5 then count:= count+1; R:= R, k*(k-1) fi;
  w:= wp;
od:
R; # Robert Israel, Jul 14 2026

Mathematica

Select[(#*(# + 1)) & /@ Range[400], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1, 1} &] (* Amiram Eldar, Dec 25 2022 *)

Prog

(PARI) select(x->((omega(x)==5) && (bigomega(x)==5)), vector(500, k, k*(k+1))) \\ Michel Marcus, Dec 25 2022

Crossrefs

Intersection of A002378 and A046387.

Sequence in context: A101619 A239255 A252555 * A233888 A204408 A204401

Adjacent sequences: A359301 A359302 A359303 * A359305 A359306 A359307

Keyword

nonn,changed

Author

Massimo Kofler, Dec 25 2022

Status

approved