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A036087
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Centered cube numbers: (n+1)^9+n^9.
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6
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1, 513, 20195, 281827, 2215269, 12030821, 50431303, 174571335, 521638217, 1387420489, 3357947691, 7517728043, 15764279725, 31265546157, 59104406159, 107162836111, 187307353233, 316947166865
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Never prime nor semiprime, as a(n) = (2n+1) * (n^2 + n + 1) * (n^6 + 3n^5 + 12n^4 + 19n^3 + 15n^2 + 6n + 1) [Jonathan Vos Post, Aug 26 2011].
Three-almost primes (A014612) if n=2, 5, 6, 14, 21, 75, 90,... [R. J. Mathar, Aug 27 2011]
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REFERENCES
| B. K. Teo and N. J. A. Sloane, Magic numbers in polygonal and polyhedral clusters, Inorgan. Chem. 24 (1985), 4545-4558.
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..10000
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FORMULA
| a(n) = A001017(n+1)+A001017(n).
G.f. (1+x)*(x^8 +502*x^7 +14608*x^6 +88234*x^5 +156190*x^4 +88234*x^3 +14608*x^2 +502*x+1) / (x-1)^10 . - R. J. Mathar, Aug 27 2011
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PROG
| (MAGMA) [(n+1)^9+n^9: n in [0..20]]; // Vincenzo Librandi, Aug 27 2011
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CROSSREFS
| Cf. A036085, A100267, A154535, A100266, A152913, A194155, A194185, A194216.
Sequence in context: A111344 A017681 A013957 * A007487 A023878 A168118
Adjacent sequences: A036084 A036085 A036086 * A036088 A036089 A036090
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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