id:A062380 - OEIS Search Results

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a(n) = Sum_{i|n,j|n} phi(i)*phi(j)/phi(gcd(i,j)), where phi is Euler totient function.

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1, 4, 7, 14, 13, 28, 19, 42, 37, 52, 31, 98, 37, 76, 91, 114, 49, 148, 55, 182, 133, 124, 67, 294, 113, 148, 163, 266, 85, 364, 91, 290, 217, 196, 247, 518, 109, 220, 259, 546, 121, 532, 127, 434, 481, 268, 139, 798, 229, 452, 343, 518, 157, 652, 403, 798, 385 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Multiplicative with a(p^e) = 1+ sum_{k=1..e} (2k+1)(p^k-p^{k-1}) = ((2e+1)p^(e+1)-(2e+3)p^e+2)/(p-1) Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu) May 24, 2005.`
	FORMULA	`a(n) = Sum_{d\|n} phi(d)*tau(d^2).`
	CROSSREFS	`Cf. A000005, A000010, A060648.` `Sequence in context: A074862 A101064 A055675 this_sequence A072031 A007437 A049766` `Adjacent sequences: A062377 A062378 A062379 this_sequence A062381 A062382 A062383`
	KEYWORD	`nonn,mult`
	AUTHOR	`Vladeta Jovovic (vladeta(AT)Eunet.yu), Jul 07 2001`

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Last modified July 4 18:25 EDT 2008. Contains 140886 sequences.

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