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A036085 Centered cube numbers: (n+1)^7+n^7. 9
1, 129, 2315, 18571, 94509, 358061, 1103479, 2920695, 6880121, 14782969, 29487171, 55318979, 98580325, 168162021, 276272879, 439294831, 678774129, 1022558705, 1506091771, 2173871739, 3081088541, 4295446429, 5899183335, 7991296871, 10689987049, 14135325801 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Never prime, as a(n) = (2n+1)*(n^6 + 3n^5 + 9n^4 + 13n^3 + 11n^2 + 5n + 1).  Semiprimes in the sequence begin for n = 1, 2, 8, 9, 21, 30, 33, 53, 65, 81, 83. -  Jonathan Vos Post, Aug 26 2011

REFERENCES

B. K. Teo and N. J. A. Sloane, Magic numbers in polygonal and polyhedral clusters, Inorgan. Chem. 24 (1985), 4545-4558.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..10000

Index entries for linear recurrences with constant coefficients, signature (8,-28,56,-70,56,-28,8,-1).

FORMULA

a(n) = A001015(n+1)+A001015(n).

G.f. (1+x)*(x^6 +120*x^5 +1191*x^4 +2416*x^3 +1191*x^2 +120*x+1) / (x-1)^8 . - R. J. Mathar, Aug 27 2011

PROG

(MAGMA) [(n+1)^7+n^7: n in [0..30]]; // Vincenzo Librandi, Aug 27 2011

(PARI) a(n)=(n+1)^7+n^7 \\ Charles R Greathouse IV, Oct 07 2015

CROSSREFS

Cf. A100267, A154535, A100266, A152913, A194155, A194185, A194216.

Sequence in context: A017677 A013955 A221969 * A000541 A023876 A279640

Adjacent sequences:  A036082 A036083 A036084 * A036086 A036087 A036088

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified August 20 13:04 EDT 2017. Contains 290835 sequences.