A164004 Zero together with row 4 of the array in A163280.

0, 5, 10, 18, 28, 40, 54, 70, 88, 108, 130, 154, 180, 208, 238, 270, 304, 340, 378, 418, 460, 504, 550, 598, 648, 700, 754, 810, 868, 928, 990, 1054, 1120, 1188, 1258, 1330, 1404, 1480, 1558, 1638, 1720, 1804, 1890, 1978, 2068, 2160, 2254, 2350, 2448, 2548

Offset

0,2

Links

G. C. Greubel, Table of n, a(n) for n = 0..5000

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

Formula

Conjectures from Colin Barker, Apr 07 2015: (Start)

a(n) = n*(3+n) = A028552(n) for n > 1.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 4.

G.f.: x*(x^3 - 3*x^2 + 5*x - 5) / (x-1)^3. (End)

E.g.f.: x*(x+4)*exp(x) + x. - G. C. Greubel, Aug 28 2017

Maple

A033676 := proc(n) local a, d; a := 0 ; for d in numtheory[divisors](n) do if d^2 <= n then a := max(a, d) ; fi; od: a; end: A163280 := proc(n, k) local r, T ; r := 0 ; for T from k^2 by k do if A033676(T) = k then r := r+1 ; if r = n then RETURN(T) ; fi; fi; od: end: A164004 := proc(n) if n = 0 then 0; else A163280(4, n) ; fi; end: seq(A164004(n), n=0..80) ; # R. J. Mathar, Aug 09 2009

Mathematica

Join[{0, 5}, Table[n*(n + 3), {n, 2, 50}]] (* G. C. Greubel, Aug 28 2017 *)

Prog

(PARI) x='x+O('x^50); concat([0], Vec(x*(x^3 -3*x^2 +5*x -5)/(x-1)^3)) \\ G. C. Greubel, Aug 28 2017

Crossrefs

Cf. A008578, A161344, A161345, A163280, A164000, A005563, A164005.

Cf. A028552.

Sequence in context: A092390 A035608 A091386 * A025010 A299144 A058555

Adjacent sequences: A164001 A164002 A164003 * A164005 A164006 A164007

Keyword

nonn,easy,less

Author

Omar E. Pol, Aug 08 2009

Extensions

Extended beyond a(12) by R. J. Mathar, Aug 09 2009

Status

approved