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 A076971 a(1) = 1, a(n+1)= smallest triangular number greater than the n-th partial sum. 1
 1, 3, 6, 15, 28, 55, 120, 231, 465, 946, 1891, 3828, 7626, 15225, 30628, 61075, 122265, 244650, 489555, 979300, 1959210, 3918600, 7838820, 15677200, 31359240, 62714400, 125429041, 250868800, 501732003, 1003497600, 2006959690 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS MAPLE a[1] := 1:a[2] := 3:for n from 3 to 145 do a[n] := sum(a[i], i=1..n-1); a[n] := ceil(evalf(-1/2+1/2*sqrt(1+8*a[n])+10^(-19), 100)):a[n] := a[n]*(a[n]+1)/2: od:seq(a[k], k=1..145); CROSSREFS Cf. A076972. Sequence in context: A234848 A300761 A069712 * A103529 A185378 A285563 Adjacent sequences:  A076968 A076969 A076970 * A076972 A076973 A076974 KEYWORD nonn AUTHOR Amarnath Murthy, Oct 21 2002 EXTENSIONS More terms from Sascha Kurz, Jan 22 2003 STATUS approved

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Last modified August 3 14:45 EDT 2020. Contains 336198 sequences. (Running on oeis4.)