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A091369 a(n) = Sum_{i=1..n} phi(i)*ceiling(n/i). 2
1, 3, 7, 12, 20, 27, 39, 50, 64, 77, 97, 112, 136, 155, 177, 200, 232, 255, 291, 318, 350, 381, 425, 456, 500, 537, 581, 620, 676, 713, 773, 820, 872, 921, 979, 1026, 1098, 1153, 1215, 1270, 1350, 1403, 1487, 1550, 1618, 1685, 1777, 1840, 1930, 1999, 2081, 2156 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..52.

FORMULA

a(n) = n^2 - A063985(n). - Enrique Pérez Herrero, Feb 25 2012

MAPLE

A091369:=n->add(numtheory[phi](i)*ceil(n/i), i=1..n): seq(A091369(n), n=1..100); # Wesley Ivan Hurt, Apr 13 2017

MATHEMATICA

A091369[n_] := Sum[EulerPhi[i]*Ceiling[n/i], {i, n}] (* Robert G. Wilson v, Mar 02 2004 *)

PROG

(PARI) a(n) = sum(k=1, n, eulerphi(k)*ceil(n/k)); \\ Michel Marcus, Apr 13 2017

CROSSREFS

Cf. A000217, A063985.

Sequence in context: A011899 A002498 A172115 * A036698 A279169 A132273

Adjacent sequences:  A091366 A091367 A091368 * A091370 A091371 A091372

KEYWORD

nonn,easy

AUTHOR

Jon Perry, Mar 01 2004

EXTENSIONS

More terms from Robert G. Wilson v, Mar 02 2004

STATUS

approved

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Last modified January 20 02:29 EST 2018. Contains 297938 sequences.