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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A185980 Nontriangular numbers that are the sum of two (positive) triangular numbers in more than one way.

Original entry on oeis.org

16, 31, 42, 46, 51, 56, 72, 76, 81, 94, 106, 111, 121, 123, 126, 133, 141, 146, 156, 157, 172, 174, 181, 186, 191, 196, 198, 211, 216, 225, 226, 237, 241, 246, 256, 259, 268, 281, 286, 289, 291, 297, 301, 306, 310, 315, 321, 326, 328, 331, 336, 342, 346, 354
Offset: 1

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Author

Wolfdieter Lang, Feb 15 2011

Keywords

Comments

A000217(0)=0, but it will not appear as a summand.
A185979 uses only positive triangular summands, and includes triagonal (or body diagonal) numbers like 231, 276, 406, 666, ...

Examples

			16 = 15 + 1 = 10 + 6.
81 = 45 + 36 = 66 + 15 = 78 + 3.

Crossrefs

Cf. A000217, A020756 (sums of two triangular numbers), A051533 (sums of two positive triangular numbers), A064816, A185978, A185979.

Formula

See the one given for A185978, taking into account multiplicities.
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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