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A064816
Numbers which are the sums of two positive triangular numbers (A000217) in exactly two different ways.
10
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
OFFSET
1,1
COMMENTS
Note that A000217(0)=0, so even 6 = 6 + 0 = 3 + 3, it is not a member of this sequence. - Wolfdieter Lang, Feb 15 2011
LINKS
EXAMPLE
16 = 15 + 1 = 10 + 6.
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)) ) } \\ Harry J. Smith, Sep 27 2009
CROSSREFS
Sequence in context: A167997 A185979 A185980 * A262749 A265134 A220000
KEYWORD
nonn
AUTHOR
Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 22 2001
EXTENSIONS
Offset changed from 0 to 1 by Harry J. Smith, Sep 27 2009
Name corrected by Wolfdieter Lang, Feb 15 2011
STATUS
approved