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Search: id:A061317
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| A061317 |
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Split positive integers into extending even groups and sum: 1+2, 3+4+5+6, 7+8+9+10+11+12, 13+14+15+16+17+18+19+20,... |
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+0
3
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| 0, 3, 18, 57, 132, 255, 438, 693, 1032, 1467, 2010, 2673, 3468, 4407, 5502, 6765, 8208, 9843, 11682, 13737, 16020, 18543, 21318, 24357, 27672, 31275, 35178, 39393, 43932, 48807, 54030, 59613, 65568, 71907, 78642, 85785, 93348, 101343, 109782
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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Harry J. Smith, Table of n, a(n) for n=0,...,1000
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FORMULA
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a(n) =2n^3+n =A000217(A002378(n))-A000217(A002378(n-1)) =3*A005900(n) =A001477(n)*A058331(n) =A000578(n)+A034262(n)
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EXAMPLE
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1+2=3; 3+4+5+6=18; 7+8+9+10+11+12=57; 13+14+15+16+17+18+19+20=132
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PROGRAM
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(PARI) { for (n=0, 1000, write("b061317.txt", n, " ", 2*n^3 + n) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 21 2009]
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CROSSREFS
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Cf. A005898, A006003.
Sequence in context: A027334 A130505 A027289 this_sequence A139362 A012763 A006011
Adjacent sequences: A061314 A061315 A061316 this_sequence A061318 A061319 A061320
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KEYWORD
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nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Feb 13 2002
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