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A068882
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Triangular numbers with property that digits alternate in parity.
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8
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1, 3, 6, 10, 21, 36, 45, 78, 105, 210, 276, 325, 496, 561, 630, 703, 741, 903, 1830, 2145, 2701, 5050, 6105, 6903, 8385, 9870, 10585, 12561, 14365, 18145, 18721, 23436, 25878, 29890, 30381, 32385, 36585, 38503, 38781, 41616, 47278, 50721
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OFFSET
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1,2
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LINKS
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EXAMPLE
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1830 is a term as 1, 8, 3 and 0 have odd and even parity alternately.
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MATHEMATICA
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altQ[n_] := n < 10 || Union[ Total /@ Partition[ Mod[ IntegerDigits@n, 2], 2, 1]] == {1}; t[n_] := n (n + 1)/2; Select[ t@ Range@ 400, altQ] (* Giovanni Resta, Aug 17 2018 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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