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A064816
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Numbers which are the sums of two positive triangular numbers (A000217) in exactly two different ways.
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8
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16, 31, 42, 46, 51, 56, 72, 76, 94, 111, 121, 123, 126, 133, 141, 146, 157, 172, 174, 186, 191, 196, 198, 216, 225, 226, 231, 237, 241, 246, 259, 268, 281, 286, 289, 291, 297, 301, 306, 310, 315, 321, 326, 328, 336, 342, 346, 354, 366, 367, 379, 380, 384
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Note that A000217(0)=0, so even 6 = 6 + 0 = 3 + 3, it is not a member of this sequence.
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,1000
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EXAMPLE
| 16 = 15 + 1 = 10 + 6.
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PROG
| (PARI) Tri(n)= { n*(n + 1)/2 } { n=0; for (m=1, 10^9, k=0; i=1; until (t>=m\2 || k>2, t=Tri(i); j=i; i++; until (s>=m || k>2, s=t + Tri(j); j++; if (s==m, k++))); if (k==2, write("b064816.txt", n++, " ", m); if (n==1000, return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 27 2009]
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CROSSREFS
| Sequence in context: A167997 A185979 A185980 * A132299 A059164 A040240
Adjacent sequences: A064813 A064814 A064815 * A064817 A064818 A064819
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KEYWORD
| nonn
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AUTHOR
| Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 22 2001
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EXTENSIONS
| Offset changed from 0 to 1 by Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 27 2009
Name corrected and comment added by Wolfdieter Lang, Feb 15 2011.
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