%I #6 Dec 15 2022 13:56:46
%S 4,7,9,16,31,48,28,160,54,512,128,512,946,4224,512,10240,11566,4095,
%T 1024,65535,94794,180224,22796,262143,1048575,7077888,1339848
%N a(n) is the index of the smallest n-gonal pyramidal number with exactly n prime factors (counted with multiplicity).
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PrimeFactor.html">Prime Factor</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PyramidalNumber.html">Pyramidal Number</a>
%o (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
%Y Cf. A358865, A359015.
%K nonn,more
%O 3,1
%A _Ilya Gutkovskiy_, Dec 12 2022
%E a(27)-a(29) from _Daniel Suteu_, Dec 12 2022