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A340683
a(n) = A007949((A003961(A003961(n))+1)/2), where A003961 shifts the prime factorization of n one step towards larger primes, and A007949(x) gives the exponent of largest power of 3 dividing x.
2
0, 1, 0, 0, 1, 2, 0, 2, 0, 0, 2, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 2, 0, 0, 0, 0, 0, 1, 1, 3, 1, 3, 1, 1, 0, 0, 1, 4, 0, 0, 1, 0, 1, 1, 1, 0, 2, 2, 0, 0, 0, 1, 0, 0, 2, 0, 0, 0, 1, 1, 3, 0, 1, 1, 2, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 1, 0, 2, 1, 0, 3, 0, 0, 3, 1
OFFSET
1,6
FORMULA
PROG
(PARI)
A003961(n) = { my(f=factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); }; \\ From A003961
A340683(n) = valuation((A003961(A003961(n))+1)/2, 3);
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 14 2021
STATUS
approved