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A064825 Numbers which are the sums of three positive triangular numbers in exactly two different ways. 6
12, 17, 19, 21, 22, 23, 26, 27, 28, 31, 32, 33, 34, 35, 39, 41, 42, 43, 44, 46, 47, 51, 54, 56, 62, 64, 65, 68, 74, 80, 88, 89, 90, 92, 95, 106, 113, 123, 128, 137, 141, 146, 153, 164, 179, 194, 200, 218, 245, 281, 326, 335 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Checked up to 1000000 but haven't found any other values.

A063993(a(n)) = 2. - Reinhard Zumkeller, Jul 20 2012

Without the qualifier "positive" in the Name, sequence A071530 would result. - Jon E. Schoenfield, Jan 01 2020

LINKS

Table of n, a(n) for n=1..52.

EXAMPLE

19 = 10 + 6 + 3 = 15 + 3 + 1.

PROG

(MAGMA) [k:k in [1..350]|#RestrictedPartitions(k, 3, {m*(m+1) div 2:m in [1..200]}) eq 2 ]; // Marius A. Burtea, Jan 01 2020

CROSSREFS

Cf. A063993, A064816, A002097, A071530, A111638.

Sequence in context: A248478 A059390 A179243 * A162918 A105018 A154488

Adjacent sequences:  A064822 A064823 A064824 * A064826 A064827 A064828

KEYWORD

nonn

AUTHOR

Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 23 2001

EXTENSIONS

Offset changed to 1 by Michel Marcus, Jan 14 2014

STATUS

approved

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Last modified July 28 07:21 EDT 2021. Contains 346318 sequences. (Running on oeis4.)