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A134154 a(n) = 15n^2 - 9n + 1. 11
1, 7, 43, 109, 205, 331, 487, 673, 889, 1135, 1411, 1717, 2053, 2419, 2815, 3241, 3697, 4183, 4699, 5245, 5821, 6427, 7063, 7729, 8425, 9151, 9907, 10693, 11509, 12355, 13231, 14137, 15073, 16039, 17035, 18061, 19117, 20203, 21319, 22465, 23641 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

A119617 is union of A134153 and A134154 A000538(n) is divisible by A000330(n) if and only n is congruent to {1, 3} mod 5 (see A047219) A134154(n) is case when n is congruent to 3 mod 5 see cases 2)

LINKS

Table of n, a(n) for n=0..40.

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

1) a(n) = 15n^2 - 9n + 1 2) a(n) = (3(5n + 3)^2 + 3 (5n + 3) - 1)/5 3) a(n) = sum[k^4]/sum[k^2], {k, 1, 5m + 3}]

G.f.: -(1+4*x+25*x^2)/(-1+x)^3. - R. J. Mathar, Nov 14 2007

MATHEMATICA

1) Table[1 - 9 n + 15 n^2, {n, 0, 50}] 2) Table[Sum[k^4, {k, 1, 5m + 3}]/Sum[k^2, {k, 1, 5m + 3}], {m, 0, 30}] (*Artur Jasinski*)

PROG

(PARI) a(n)=15*n^2-9*n+1 \\ Charles R Greathouse IV, Jun 17 2017

CROSSREFS

Cf. A000538, A119617, A134153.

Sequence in context: A172469 A216301 A201717 * A183537 A114352 A201707

Adjacent sequences:  A134151 A134152 A134153 * A134155 A134156 A134157

KEYWORD

nonn,easy

AUTHOR

Artur Jasinski, Oct 10 2007

STATUS

approved

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Last modified September 26 11:22 EDT 2021. Contains 347665 sequences. (Running on oeis4.)