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A351567
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The second least significant nonzero digit in the primorial base expansion of n, or 0 if there is no such digit.
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3
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0, 0, 0, 1, 0, 2, 0, 1, 1, 1, 1, 2, 0, 2, 2, 1, 2, 2, 0, 3, 3, 1, 3, 2, 0, 4, 4, 1, 4, 2, 0, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 3, 3, 1, 3, 2, 1, 4, 4, 1, 4, 2, 0, 2, 2, 1, 2, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 1, 2, 2, 2, 3, 3, 1, 3, 2, 2, 4, 4, 1, 4, 2, 0, 3, 3, 1, 3, 2, 3, 1, 1, 1, 1, 2, 3, 2, 2, 1
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OFFSET
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0,6
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LINKS
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FORMULA
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MATHEMATICA
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a[n_] := Module[{k = n, p = 2, s = {}, r}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, If[r > 0, AppendTo[s, r]]; p = NextPrime[p]]; i = Position[s, _?(# > 0 &)] // Flatten; If[Length[s] < 2, 0, s[[2]]]]; Array[a, 100, 0] (* Amiram Eldar, Mar 13 2024 *)
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PROG
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(PARI)
A351563(n) = if(1>=omega(n), 0, (factor(n))[2, 2]);
A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
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CROSSREFS
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Cf. A060735 (gives the positions of zeros after a(0)=0).
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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