A280288 Numbers n such that number of partitions of n is even and number of partitions of n into distinct parts is odd.
2, 15, 22, 26, 40, 57, 70, 100, 117, 126, 176, 187, 247, 260, 532, 551, 590, 651, 715, 782, 925, 950, 1001, 1027, 1080, 1107, 1162, 1276, 1365, 1457, 1520, 1552, 1650, 1751, 1820, 1926, 2072, 2185, 2262, 2301, 2380, 2420, 2501, 2667, 2752, 2926, 3015, 3060, 3151, 3290, 3432, 3577, 3725, 3927, 4082, 4187, 4240, 4401
Offset: 1
Examples
15 is in the sequence because we have: ------------------------------------ number of partitions = 176 (is even) ------------------------------------ 15 = 15 14 + 1 = 15 13 + 2 = 15 13 + 1 + 1 = 15 12 + 3 = 15 12 + 2 + 1 = 15 12 + 1 + 1 + 1 = 15 11 + 4 = 15 11 + 3 + 1 = 15 11 + 2 + 2 = 15 11 + 2 + 1 + 1 = 15 11 + 1 + 1 + 1 + 1 = 15 ... ------------------------------------------------------ number of partitions into distinct parts = 27 (is odd) ------------------------------------------------------ 15 = 15 14 + 1 = 15 13 + 2 = 15 12 + 3 = 15 12 + 2 + 1 = 15 11 + 4 = 15 11 + 3 + 1 = 15 10 + 5 = 15 10 + 4 + 1 = 15 10 + 3 + 2 = 15 ...
Links
- Eric Weisstein's World of Mathematics, Partition Function P, Partition Function Q
- Index entries for related partition-counting sequences
Programs
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Mathematica
Select[Range[4500], Mod[PartitionsP[#1], 2] == 0 && Mod[PartitionsQ[#1], 2] == 1 & ]
Comments