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A065093 Convolution of A000010 with itself. 4
1, 2, 5, 8, 16, 20, 36, 44, 68, 76, 120, 124, 188, 196, 276, 272, 404, 380, 544, 532, 716, 668, 968, 860, 1184, 1120, 1472, 1332, 1896, 1624, 2204, 2036, 2656, 2352, 3284, 2752, 3684, 3356, 4324, 3744, 5192, 4312, 5720, 5180, 6540, 5628, 7768, 6388, 8476 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harry J. Smith, Table of n, a(n) for n=1,...,1000

FORMULA

Sum_{k=1..n} phi(k)*phi(n+1-k), where phi is Euler totient function (A000010).

G.f.: (1/x)*(Sum_{k>=1} mu(k)*x^k/(1 - x^k)^2)^2. - Ilya Gutkovskiy, Jan 31 2017

PROG

(PARI) { for (n=1, 1000, a=sum(k=1, n, eulerphi(k)*eulerphi(n+1-k)); write("b065093.txt", n, " ", a) ) } \\ Harry J. Smith, Oct 06 2009

CROSSREFS

Cf. A000010, A000385, A055507.

Sequence in context: A257548 A186413 A080084 * A168470 A295998 A129299

Adjacent sequences:  A065090 A065091 A065092 * A065094 A065095 A065096

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Nov 11 2001

STATUS

approved

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Last modified November 16 17:04 EST 2019. Contains 329201 sequences. (Running on oeis4.)