A359017 a(n) is the index of the smallest triangular number with exactly n distinct prime factors.
1, 2, 3, 11, 20, 84, 455, 1364, 10659, 58695, 254540, 728364, 13516580, 133595384, 812646120, 5327923964, 68971338435, 838101203939, 7588384207404, 69322940121435, 490005293940084
Offset: 0
Links
- Eric Weisstein's World of Mathematics, Distinct Prime Factors
- Eric Weisstein's World of Mathematics, Triangular Number
Programs
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PARI
a(n) = my(k=1); while(omega(k*(k+1)/2) != n, k++); k; \\ Michel Marcus, Feb 26 2023
Extensions
a(19)-a(20) from Michael S. Branicky, Feb 25 2023