id:A064368 - OEIS Search Results

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Number of 2 X 2 symmetric singular matrices with entries from {0,...,n}.

+0
2

1, 4, 7, 10, 15, 18, 21, 24, 29, 36, 39, 42, 47, 50, 53, 56, 65, 68, 75, 78, 83, 86, 89, 92, 97, 108, 111, 118, 123, 126, 129, 132, 141, 144, 147, 150, 163, 166, 169, 172, 177, 180, 183, 186, 191, 198, 201, 204, 213, 228, 239, 242, 247, 250, 257, 260, 265, 268 (list; graph; listen)

	OFFSET	`0,2`
	FORMULA	`a(n) = n+1+2*Sum_{k=0..n} Sum_{d^2\|k} phi(d), where phi = Euler totient function A000010.`
	CROSSREFS	`Cf. A000188, A064276, A059306, A062801, A059976, A039623.` `Adjacent sequences: A064365 A064366 A064367 this_sequence A064369 A064370 A064371` `Sequence in context: A123384 A138813 A133497 this_sequence A026372 A014690 A126891`
	KEYWORD	`nonn`
	AUTHOR	`Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 27 2001`

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Last modified October 13 20:18 EDT 2008. Contains 145016 sequences.

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