A017643 a(n) = (12n+10)^3.

1000, 10648, 39304, 97336, 195112, 343000, 551368, 830584, 1191016, 1643032, 2197000, 2863288, 3652264, 4574296, 5639752, 6859000, 8242408, 9800344, 11543176, 13481272, 15625000, 17984728, 20570824, 23393656, 26463592, 29791000, 33386248, 37259704

Offset

0,1

Comments

6n + 5 = (12n + 10) / 2 is never a square, as 5 is not a quadratic residue modulo 6. Using this, we can show that each term has an even square part and an even squarefree part, neither part being a power of 2. (Less than 2% of integers have this property - see A339245.) - Peter Munn, Dec 14 2020

Links

Table of n, a(n) for n=0..27.

Eric Weisstein's World of Mathematics, Quadratic Residue.

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

Formula

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) with a(0)=1000, a(1)=10648, a(2)=39304, a(3)=97336. [Harvey P. Dale, Sep 30 2011]

a(n) = A017641(n)^3 = A000578(A017641(n)). - Michel Marcus, Nov 25 2013

Maple

A017643:=(12*n+10)^3; seq(A017643(n), n=0..100); # Wesley Ivan Hurt, Nov 25 2013

Mathematica

(12Range[0, 30]+10)^3 (* or *) LinearRecurrence[{4, -6, 4, -1}, {1000, 10648, 39304, 97336}, 30] (* Harvey P. Dale, Sep 30 2011 *)

Crossrefs

A000578, A017641 are used in a formula defining this sequence.

Subsequence of A339245.

Cf. A017642, A017644.

Sequence in context: A017271 A017511 A326639 * A161770 A004632 A277397

Adjacent sequences: A017640 A017641 A017642 * A017644 A017645 A017646

Keyword

nonn,easy

Author

N. J. A. Sloane.

Status

approved