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 A249020 a(n) = floor( n * (n+5) / 10) + 1. 2
 1, 1, 2, 3, 4, 6, 7, 9, 11, 13, 16, 18, 21, 24, 27, 31, 34, 38, 42, 46, 51, 55, 60, 65, 70, 76, 81, 87, 93, 99, 106, 112, 119, 126, 133, 141, 148, 156, 164, 172, 181, 189, 198, 207, 216, 226, 235, 245, 255, 265, 276, 286, 297, 308, 319, 331, 342, 354, 366 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS G. C. Greubel, Table of n, a(n) for n = 0..2500 Peter H. van der Kamp, Somos-4 and Somos-5 are arithmetic divisibility sequences, arXiv:1505.00194 [math.NT], 2015. Index entries for linear recurrences with constant coefficients, signature (2,-1,0,0,1,-2,1). FORMULA G.f.: (1 - x + x^2) / ((1 - x)^2 * (1 - x^5)). Euler transform of length 6 sequence [ 1, 1, 1, 0, 1, -1]. - Michael Somos, Oct 19 2014 a(n) = a(-5-n) for all n in Z. a(n) = a(n-5) + n for all n in Z. a(n) + a(n+4) = min( a(n+1) + a(n+3), a(n+2) + a(n+2)) + 1 for all n in Z. a(n) = A249013(n+1) + 1 for all n in Z. a(n) = A008669(n) - A008669(n-6) for all n in Z. EXAMPLE G.f. = 1 + x + 2*x^2 + 3*x^3 + 4*x^4 + 6*x^5 + 7*x^6 + 9*x^7 + ... MATHEMATICA a[ n_] := Quotient[ n (n + 5), 10] + 1; CoefficientList[Series[(1-x+x^2)/((1-x)^2*(1-x^5)), {x, 0, 60}], x] (* or *) Table[Floor[n*(n+5)/10]+1, {n, 0, 60}] (* G. C. Greubel, Aug 04 2018 *) PROG (PARI) {a(n) = n * (n + 5) \ 10 + 1}; (PARI) {a(n) = if( n<0, n = -5-n); polcoeff( (1 - x + x^2) / ((1 - x)^2 * (1 - x^5)) + x * O(x^n), n)}; (MAGMA) [Floor(n*(n+5)/10) + 1: n in [0..60]]; // G. C. Greubel, Aug 04 2018 CROSSREFS Cf. A008669, A249013. Sequence in context: A085680 A253186 A321195 * A258470 A248357 A047872 Adjacent sequences:  A249017 A249018 A249019 * A249021 A249022 A249023 KEYWORD nonn,easy AUTHOR Michael Somos, Oct 19 2014 STATUS approved

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Last modified April 19 09:16 EDT 2019. Contains 322241 sequences. (Running on oeis4.)