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A328828
Index of the least significant digit larger than one in the primorial base expansion of n, 0 if no such digit exists.
7
0, 0, 0, 0, 2, 2, 0, 0, 0, 0, 2, 2, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 2, 2, 0, 0, 0, 0, 2, 2, 0, 0, 0, 0, 2, 2, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 2, 2, 4, 4, 4, 4, 2, 2, 4, 4, 4, 4, 2, 2, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 2, 2, 4, 4, 4, 4, 2, 2, 4, 4, 4, 4, 2, 2, 3, 3, 3, 3
OFFSET
0,5
FORMULA
a(n) = A277885(A276086(n)) = A055396(A328572(n)).
MATHEMATICA
a[n_] := Module[{k = n, p = 2, s = {}, r, i}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, AppendTo[s, r]; p = NextPrime[p]]; i = FirstPosition[s, _?(# > 1 &)]; If[MissingQ[i], 0, i[[1]]]]; Array[a, 100] (* Amiram Eldar, Mar 13 2024 *)
PROG
(PARI) A328828(n) = { my(i=1, p=2); while(n, if((n%p)>1, return(i)); i++; n = n\p; p = nextprime(1+p)); (0); };
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Antti Karttunen, Oct 29 2019
STATUS
approved