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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
 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 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 January 30 19:55 EST 2023. Contains 359947 sequences. (Running on oeis4.)