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 A252747 Numbers n such that the hexagonal number H(n) is equal to the sum of four consecutive squares. 2
 18, 42, 602, 1418, 20442, 48162, 694418, 1636082, 23589762, 55578618, 801357482, 1888036922, 27222564618, 64137676722, 924765839522, 2178792971618, 31414815979122, 74014823358282, 1067178977450618, 2514325201209962, 36252670417341882, 85413042017780418 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also positive integers y in the solutions to 8*x^2-4*y^2+24*x+2*y+28 = 0, the corresponding values of x being A201633. LINKS Colin Barker, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (1,34,-34,-1,1). FORMULA a(n) = a(n-1)+34*a(n-2)-34*a(n-3)-a(n-4)+a(n-5). G.f.: -2*x*(x^4-26*x^2+12*x+9) / ((x-1)*(x^2-6*x+1)*(x^2+6*x+1)). EXAMPLE 18 is in the sequence because H(18) = 630 = 121+144+169+196 = 11^2+12^2+13^2+14^2. PROG (PARI) Vec(-2*x*(x^4-26*x^2+12*x+9)/((x-1)*(x^2-6*x+1)*(x^2+6*x+1)) + O(x^100)) CROSSREFS Cf. A000290, A000384, A201633, Sequence in context: A144737 A333457 A304152 * A067750 A043362 A023735 Adjacent sequences: A252744 A252745 A252746 * A252748 A252749 A252750 KEYWORD nonn,easy AUTHOR Colin Barker, Dec 21 2014 STATUS approved

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Last modified February 25 06:40 EST 2024. Contains 370310 sequences. (Running on oeis4.)