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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 are the triangular numbers (A000217). 1
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) = row sums of triangle A143267.

a(n)=n(n+1)phi(n)/2. [From 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); [From 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 November 13 01:32 EST 2018. Contains 317118 sequences. (Running on oeis4.)