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Search: id:A078522
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| A078522 |
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Numbers n such that (n+1)(2n+1) is a perfect square. Equivalently, both n+1 and 2n+1 are perfect squares. |
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+0
2
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| 0, 24, 840, 28560, 970224, 32959080, 1119638520, 38034750624, 1292061882720, 43892069261880, 1491038293021224, 50651409893459760, 1720656898084610640, 58451683124983302024, 1985636569351347658200, 67453191674820837076800
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OFFSET
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1,2
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FORMULA
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a(1)=0; a(2)=24; a(n)=34*a(n-1)-a(n-2)+24; a(n)=floor(A*B^n) where A=(3+2*sqrt(2))/8 and B=17+12*sqrt(2); a(n)=A008844(n)-1. - Benoit Cloitre (benoit7848c(AT)orange.fr), Jan 19 2003
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MATHEMATICA
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a[0]=0; a[1]=24; a[n_] := a[n]=34a[n-1]-a[n-2]+24
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CROSSREFS
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The square roots of (n+1)(2n+1) are in A046176.
Adjacent sequences: A078519 A078520 A078521 this_sequence A078523 A078524 A078525
Sequence in context: A105187 A062313 A062528 this_sequence A005149 A027411 A109575
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 07 2003
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