A359016 a(n) is the index of the smallest n-gonal pyramidal number with exactly n prime factors (counted with multiplicity).

4, 7, 9, 16, 31, 48, 28, 160, 54, 512, 128, 512, 946, 4224, 512, 10240, 11566, 4095, 1024, 65535, 94794, 180224, 22796, 262143, 1048575, 7077888, 1339848

Offset: 3

Author

Ilya Gutkovskiy, Dec 12 2022

Keywords

• nonn
• more

Links

• Eric Weisstein's World of Mathematics, Prime Factor
• Eric Weisstein's World of Mathematics, Pyramidal Number

Crossrefs

Cf. A358865, A359015.

Programs

PARI

a(n) = if(n<3, return()); for(k=1, oo, my(t=(k*(k+1)*((n-2)*k + (5-n)))\6); if(bigomega(t) == n, return(k))); \\ Daniel Suteu, Dec 12 2022

Extensions

a(27)-a(29) from Daniel Suteu, Dec 12 2022