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Search: id:A036557
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| A036557 |
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Number of multiples of 3 in 0..2^n-1 with an even sum of base 2 bits. |
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+0
3
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| 1, 1, 2, 3, 6, 10, 20, 35, 70, 126, 252, 463, 926, 1730, 3460, 6555, 13110, 25126, 50252, 97223, 194446, 379050, 758100, 1486675, 2973350, 5858126, 11716252, 23166783, 46333566, 91869970, 183739940, 365088395, 730176790
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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(1/12) {3^[(n+1)/2] + 3^[(n+2)/2] + 2^(n+1) + (-1)^n + 3}, n>0. G.f. -[x^5-3x^4-3x^3+4x^2+x-1]/[(1-x^2)(1-2x)(1-3x^2)]. - R. Stephan, Aug 29 2004
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MATHEMATICA
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Sum[ Sum[ Binomial[ Floor[ n/2 ], i ], {i, r, n, 6} ]*Sum[ Binomial[ Ceiling[ n/2 ], i ], {i, r, n, 6} ], {r, 0, 5} ]
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CROSSREFS
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Cf. A036555-A036557.
Sequence in context: A056202 A001405 A126930 this_sequence A047131 A008927 A052525
Adjacent sequences: A036554 A036555 A036556 this_sequence A036558 A036559 A036560
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KEYWORD
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nonn,base
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AUTHOR
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Hoey(AT)AIC.NRL.Navy.Mil
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