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A339815
Let x = A019565(2*n); a(n) is the difference between 2-adic valuations of phi(x) and (x-1).
4
0, 0, 2, 0, 0, 2, 1, 0, -3, 2, 2, 0, 2, -3, 4, 0, 2, -2, 4, 2, 0, 4, 4, 2, 2, 4, 1, 1, 4, 4, 6, 0, 4, 4, 6, 4, 4, 6, 5, 4, 2, 6, 6, 4, 6, 4, 8, 4, 6, 4, 8, 6, 3, 8, 8, 6, 6, 8, 6, 5, 8, 8, 10, 0, -1, 2, 2, 0, 2, 1, 4, -2, 2, 2, 4, 2, 2, 4, 3, 2, 2, 4, 3, -2, 4, 4, 6, 2, 4, 2, 6, 4, 1, 6, 6, 4, 3, 6, 6, 4, 6, 5, 8, 1, 6
OFFSET
1,3
LINKS
FORMULA
a(n) = A339822(n) - A339814(n).
a(n) = A007814(A000010(A019565(2n))) - A007814(A019565(2n)-1).
PROG
(PARI)
A019565(n) = { my(m=1, p=1); while(n>0, p = nextprime(1+p); if(n%2, m *= p); n >>= 1); (m); };
A339815(n) = { my(x=A019565(2*n)); valuation(eulerphi(x), 2)-valuation(x-1, 2); };
CROSSREFS
Cf. A339816 (indices of terms < 1).
Sequence in context: A303906 A178580 A035437 * A156996 A029304 A030202
KEYWORD
sign
AUTHOR
Antti Karttunen, Dec 18 2020
STATUS
approved