OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
MATHEMATICA
expQ[e1_, e2_] := Module[{m = Length[e2], ans = 1}, Do[If[BitAnd[e1[[i]], e2[[i]]] < e2[[i]], ans = 0; Break[]], {i, 1, m}]; ans];
e[n_] := e[n] = FactorInteger[n!][[;; , 2]]; a[n_] := 1 + Sum[expQ[e[n], e[m]], {m, 2, n}]; Array[a, 100]
PROG
(PARI) isexp(e1, e2) = {my(m = #e2, ans = 1); for(i=1, m, if(bitand(e1[i], e2[i]) < e2[i], ans = 0; break)); ans; }
e(n) = factor(n!)[, 2];
a(n) = 1 + sum(m = 2, n, isexp(e(n), e(m)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Aug 22 2024
STATUS
approved