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 A061208 Numbers which can be expressed as sum of distinct triangular numbers (A000217). 5
 1, 3, 4, 6, 7, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS These numbers were called "almost-triangular" numbers during the Peru's Selection Test for the XII IberoAmerican Olympiad (1998). All numbers >= 34 are almost-triangular: see link. [Bernard Schott, Feb 04 2013] LINKS R. E. Woodrow, The Olympiad Corner, No. 198, Crux Mathematicorum, v25-n4(2002), 207-208, exercise 2. EXAMPLE 25 = 1 + 3 + 6 + 15 MAPLE gf := product(1+x^(j*(j+1)/2), j=1..100): s := series(gf, x, 200): for i from 1 to 200 do if coeff(s, x, i) > 0 then printf(`%d, `, i) fi:od: CROSSREFS Cf. A000217, A007294, A051611, A051533. Complement of A053614. Sequence in context: A233334 A320300 A070762 * A325439 A183860 A298109 Adjacent sequences:  A061205 A061206 A061207 * A061209 A061210 A061211 KEYWORD nonn AUTHOR Amarnath Murthy, Apr 21 2001 EXTENSIONS Corrected and extended by James A. Sellers, Apr 24 2001 STATUS approved

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Last modified September 22 02:48 EDT 2021. Contains 347605 sequences. (Running on oeis4.)