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A125511
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Octagonal numbers of the form C*(3C - 2) with 3C - 2 = k^2 and C a composite number.
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0
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96, 225, 1408, 3400, 9633, 12936, 22016, 43681, 53600, 78408, 93633, 130625, 152776, 205408, 308481, 350208, 446216, 696008, 854400, 943041, 1250656, 1493896, 1628033, 1923201, 2085000, 2439008, 3280256, 3774408, 4041441
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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MAPLE
| Contribution from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 22 2010: (Start)
A000567 := proc(n) n*(3*n-2) ; end proc:
for n from 4 to 1600 do if not isprime(n) then if issqr(3*n-2) then printf("%d, ", A000567(n) ); end if; end if; end do: (End)
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CROSSREFS
| Cf. A124106.
Sequence in context: A115437 A110231 A108609 * A124106 A202898 A202891
Adjacent sequences: A125508 A125509 A125510 * A125512 A125513 A125514
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KEYWORD
| nonn
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AUTHOR
| Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Jan 19 2007
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EXTENSIONS
| Extended beyond 22016 by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 22 2010
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