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A182717
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Number of 2's in all partitions of 2n+1 that do not contain 1 as a part.
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2
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0, 0, 1, 3, 7, 15, 29, 53, 94, 160, 265, 430, 683, 1066, 1640, 2487, 3725, 5519, 8092, 11752, 16922, 24167, 34254, 48213, 67409, 93661, 129378, 177720, 242841, 330172, 446772, 601810, 807153, 1078081, 1434250, 1900860, 2510097, 3303003, 4331767, 5662539
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OFFSET
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0,4
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LINKS
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MAPLE
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b:= proc(n, i) option remember; local r;
if n<=0 or i<2 then 0
elif i=2 then `if`(irem(n, 2, 'r')=0, r, 0)
else b(n, i-1) +b(n-i, i)
fi
end:
a:= n-> b(2*n+1, 2*n+1):
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MATHEMATICA
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b[n_, i_] := b[n, i] = If[n <= 0 || i < 2, 0, If[i == 2, If[Mod[n, 2] == 0, Quotient[n, 2], 0], b[n, i-1] + b[n-i, i]]];
a[n_] := b[2n+1, 2n+1];
Table[Count[Flatten[Select[IntegerPartitions[2 n+1], FreeQ[#, 1]&]], 2], {n, 0, 40}] (* Harvey P. Dale, Jan 28 2022 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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