A051478 a(n) is the number of values k satisfying phi(k) = 4*n+2, n>0.
4, 2, 0, 4, 2, 0, 2, 0, 0, 4, 2, 0, 2, 2, 0, 2, 2, 0, 2, 2, 0, 0, 0, 0, 2, 2, 2, 0, 0, 0, 2, 2, 0, 2, 0, 0, 2, 0, 0, 4, 2, 0, 0, 2, 0, 0, 2, 0, 2, 0, 0, 2, 0, 0, 2, 2, 0, 0, 2, 0, 0, 2, 0, 0, 2, 0, 2, 0, 0, 2, 0, 0, 2, 0, 0, 2, 2, 0, 0, 0, 0, 2, 0, 0, 2, 2, 0, 0, 2, 0, 2, 0, 0, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 1
Keywords
Examples
phi(k) = 4*1+2 has 4 solutions (k = 7, 9, 14, 18), so a(1) = 4.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
- Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).
Programs
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PARI
a(n) = invphiNum(4*n+2); \\ Amiram Eldar, Nov 05 2024, using Max Alekseyev's invphi.gp
Comments