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Search: id:A122061
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| A122061 |
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First pentagonal number, 2nd hexagonal number, 3rd heptagonal number, 4th octagonal number and then repeat the same pattern: 5th pentagonal, 6th hexagonal, 7th heptagonal, 8th octagonal, etc. |
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+0
1
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| 1, 6, 18, 40, 35, 66, 112, 176, 117, 190, 286, 408, 247, 378, 540, 736, 425, 630, 874, 1160, 651, 946, 1288, 1680, 925, 1326, 1782, 2296, 1247, 1770, 2356, 3008, 1617, 2278, 3010, 3816, 2035, 2850, 3744, 4720, 2501, 3486, 4558, 5720, 3015, 4186, 5452
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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From a quiz.
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REFERENCES
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A. Wareham, Test Your Brain Power, Ward Lock Ltd (1995).
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FORMULA
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a(n) = n*(3*n-1)/2 if n=1 mod 4 or n*(4*n-2)/2 if n=2 mod 4 or n*(5*n-3)/2 if n=3 mod 4 or n*(6*n-4)/2 if n=0 mod 4
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PROGRAM
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(PARI) for(n=1, 60, m=(n+3)%4; print1(n*((m+3)*n-m-1)/2, ", "))
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CROSSREFS
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Cf. A060354.
Adjacent sequences: A122058 A122059 A122060 this_sequence A122062 A122063 A122064
Sequence in context: A005899 A129863 A035489 this_sequence A002411 A023658 A059834
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KEYWORD
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nonn
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AUTHOR
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Herman Jamke (hermanjamke(AT)fastmail.fm), Sep 14 2006
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