A143268 - OEIS

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A143268

a(n) = phi(n)*T(n), where phi(n) is Euler's totient function (A000010) and T(n) = n*(n+1)/2 is the n-th triangular number (A000217).

1, 3, 12, 20, 60, 42, 168, 144, 270, 220, 660, 312, 1092, 630, 960, 1088, 2448, 1026, 3420, 1680, 2772, 2530, 6072, 2400, 6500, 4212, 6804, 4872, 12180, 3720, 14880, 8448, 11220, 9520, 15120, 7992, 25308, 13338, 18720, 13120, 34440, 10836, 39732 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,2`
	LINKS	`Table of n, a(n) for n=1..43.`
	FORMULA	`a(n) = sum of n-th row of triangle A143267.` `a(n) = n(n+1)phi(n)/2. - Emeric Deutsch, Aug 23 2008`
	EXAMPLE	`a(4) = 20 = phi(4) * T(4) = 2 * 10.` `a(4) = 20 = sum of row 4 terms of triangle A143267: (2 + 4 + 6 + 8).`
	MAPLE	`with(numtheory): seq((1/2)n(n+1)*phi(n), n=1..45); # Emeric Deutsch, Aug 23 2008`
	PROG	`(PARI) a(n)=eulerphi(n)n(n+1)/2 \\ Charles R Greathouse IV, Mar 05 2013`
	CROSSREFS	`Cf. A000010, A143267.` `Sequence in context: A063102 A122576 A212760 * A193558 A256131 A080767` `Adjacent sequences: A143265 A143266 A143267 * A143269 A143270 A143271`
	KEYWORD	`nonn`
	AUTHOR	`Gary W. Adamson, Aug 03 2008`
	EXTENSIONS	`Extended by Emeric Deutsch, Aug 16 2008`
	STATUS	`approved`

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Last modified December 7 22:29 EST 2019. Contains 329850 sequences. (Running on oeis4.)