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 A039596 Numbers that are simultaneously triangular and square pyramidal. 8
 1, 55, 91, 208335 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Equivalent to 1^2 + 2^2 + 3^2 + ... + r^2 = 1 + 2 + 3 + ... + s = n for some r and s. REFERENCES Joe Roberts, Lure of the Integers, page 245 (entry for 645). David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Penguin Books, p. 108. LINKS R. Finkelstein, H. London, On triangular numbers which are sums of consecutive squares, J. Number Theory 4 (1972), 455-462. M. Gardner, Letter to N. J. A. Sloane, circa Aug 11 1980, concerning A001110, A027568, A039596, etc. H. E. Thomas Jr., Problem 5634, Amer. Math. Monthly, 75 (1968), p. 1018. EXAMPLE 1^2 + 2^2 + 3^2 + 4^2 + 5^2 = 1 + 2 + 3 + ... + 10 = 55, so 55 is in the sequence. CROSSREFS Cf. A000217, A000330, A053611, A053612. Sequence in context: A063873 A063131 A128880 * A013543 A115377 A146145 Adjacent sequences:  A039593 A039594 A039595 * A039597 A039598 A039599 KEYWORD fini,nonn,full AUTHOR EXTENSIONS Additional comments from Jud McCranie, Mar 19 2000 STATUS approved

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Last modified January 18 19:32 EST 2020. Contains 331029 sequences. (Running on oeis4.)