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 A076455 Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly two ways. 3
 5, 57, 246, 710, 1635, 3255, 5852, 9756, 15345, 23045, 33330, 46722, 63791, 85155, 111480, 143480, 181917, 227601, 281390, 344190, 416955, 500687, 596436, 705300, 828425, 967005, 1122282, 1295546, 1488135, 1701435, 1936880, 2195952, 2480181 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES Fred. Schuh, Vragen betreffende een onbepaalde vergelijking, Nieuw Tijdschrift voor Wiskunde, 52 (1964-1965) 193-198. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 FORMULA G.f.: x*(5 + 32*x + 11*x^2)/(1 - x)^5. a(n) = n*(n + 1)*(4*n^2 + 2*n - 1)/2. MAPLE seq(1/2*n*(n+1)*(4*n^2+2*n-1), n=1..40); MATHEMATICA CoefficientList[Series[(5 + 32 x + 11 x^2)/(1 - x)^5, {x, 0, 50}], x] (* Vincenzo Librandi, Dec 30 2013 *) PROG (Magma) [n*(n+1)*(4*n^2+2*n-1)/2: n in [1..50]]; // Vincenzo Librandi, Dec 30 2013 CROSSREFS Cf. A002417, A076454-A076459. Sequence in context: A363059 A163793 A226425 * A196650 A197454 A196340 Adjacent sequences: A076452 A076453 A076454 * A076456 A076457 A076458 KEYWORD nonn,easy AUTHOR Floor van Lamoen, Oct 13 2002 STATUS approved

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Last modified July 20 20:50 EDT 2024. Contains 374459 sequences. (Running on oeis4.)