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A262251 Triangular numbers representable as 2^x + 3^y. 1
3, 10, 28, 91 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No other terms such that 0 <= x,y < 2000.

LINKS

Table of n, a(n) for n=1..4.

EXAMPLE

a(1) = 3 = 2^1 + 3^0.

a(4) = 91 = 2^6 + 3^3.

PROG

(PARI) isok(t) = {for (k=0, logint(t, 2), my(tt = t - 2^k); if (tt, p = valuation(tt, 3); if (tt == 3^p, return(1))); ); }

lista(nn) = for (n=1, nn, if (isok(t=n*(n+1)/2), print1(t, ", "))); \\ Michel Marcus, Sep 20 2015

CROSSREFS

Cf. A000217, A225390, A226499, A227027, A259745, A259746, A262242.

Sequence in context: A104574 A307063 A239885 * A246974 A278294 A260811

Adjacent sequences:  A262248 A262249 A262250 * A262252 A262253 A262254

KEYWORD

nonn,more

AUTHOR

Alex Ratushnyak, Sep 16 2015

STATUS

approved

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Last modified November 14 14:43 EST 2019. Contains 329126 sequences. (Running on oeis4.)