phi(n), where phi(n) is multiplicative with phi(2) = 1; phi(4) = 2; phi(2^a) = 2^(a-2)+2 if a>2; phi(p^a) = (p-1)*p^(a-1)/2 if prime p>2 and a>0.
1, 1, 2, 2, 3, 2, 4, 4, 4, 3, 6, 4, 7, 4, 6, 6, 9, 4, 10, 6, 8, 6, 12, 8, 11, 7, 10, 8, 15, 6, 16
3 seqfan posts
Tue Sep 7 11:00:42 CEST 2010 [seqfan] Re: A007987 ? was Re: Re: Number of solutions of a*b + c*d + ... + y*z = 0 (mod n)
Tue Sep 7 03:17:01 CEST 2010 [seqfan] A007987 ? was Re: Re: Number of solutions of a*b + c*d + ... + y*z = 0 (mod n)
Mon Sep 6 18:14:15 CEST 2010 [seqfan] Re: Number of solutions of a*b + c*d + ... + y*z = 0 (mod n)
Index of A-numbers in seqfan: by ascending order
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