



1, 21, 73, 157, 273, 421, 601, 813, 1057, 1333, 1641, 1981, 2353, 2757, 3193, 3661, 4161, 4693, 5257, 5853, 6481, 7141, 7833, 8557, 9313, 10101, 10921, 11773, 12657, 13573, 14521, 15501, 16513, 17557, 18633, 19741, 20881, 22053, 23257, 24493
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OFFSET

0,2


COMMENTS

5th row of A082039 Case k=4 of family T(n,k)=k^2n^2+kn+1.
Also sequence found by reading the segment (1, 21) together with the line from 21, in the direction 21, 73,..., in the square spiral whose vertices are the generalized decagonal numbers A074377.  Omar E. Pol, Nov 02 2012


LINKS

Table of n, a(n) for n=0..39.
Index entries for linear recurrences with constant coefficients, signature (3,3,1).


FORMULA

G.f.: ( 118*x13*x^2 ) / (x1)^3 .  R. J. Mathar, Dec 03 2014


PROG

(PARI) a(n)=16*n^2+4*n+1 \\ Charles R Greathouse IV, Jun 17 2017


CROSSREFS

Cf. A082040, A054569.
Sequence in context: A240824 A109357 A283802 * A316887 A296155 A218960
Adjacent sequences: A082038 A082039 A082040 * A082042 A082043 A082044


KEYWORD

easy,nonn


AUTHOR

Paul Barry, Apr 02 2003


STATUS

approved



