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

3,1

Links

Table of n, a(n) for n=3..29.

Eric Weisstein's World of Mathematics, Prime Factor

Eric Weisstein's World of Mathematics, Pyramidal Number

Prog

(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

Crossrefs

Cf. A358865, A359015.

Sequence in context: A271542 A010424 A044903 * A281144 A103073 A166742

Adjacent sequences: A359013 A359014 A359015 * A359017 A359018 A359019

Keyword

nonn,more

Author

Ilya Gutkovskiy, Dec 12 2022

Extensions

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

Status

approved