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 A144853 Coefficients in the expansion of the sine lemniscate function. 6
 1, 1, 21, 2541, 1023561, 1036809081, 2219782435101, 8923051855107621, 61797392100611962641, 690766390156657904866161, 11839493254591562294152214181, 298556076626963858753929987732701, 10706038142052878970311146962646277721, 530588758323899225681861502684757146635241 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Denoted \alpha_n by Lomont and Brillhart on page xii. REFERENCES J. S. Lomont and J. Brillhart, Elliptic Polynomials, Chapman and Hall, 2001; see p. 87. LINKS N. J. A. Sloane, Table of n, a(n) for n = 0..100 P. Bala, A triangle for calculating A144853 FORMULA E.g.f.: sl(x) = Sum_{k>=0} (-12)^k * a(k) * x^(4*k + 1) / (4*k + 1)! where sl(x) = sin lemn(x) is the sine lemniscate function of Gauss. - Michael Somos, Apr 25 2011 a(0) = 1, a(n + 1) = (1 / 3) * Sum_{j=0..n} binomial( 4*n + 3, 4*j + 1) * a(j) * b(n - j) where b() is A144849. G.f.: 1 / (1 - b(1)*x / (1 - b(2)*x / (1 - b(3)*x / ... ))) where b = A187756. - Michael Somos, Jan 03 2013 EXAMPLE G.f. = 1 + x + 21*x^2 + 2541*x^3 + 1023561*x^4 + 1036809081*x^5 + ... MAPLE for n from 1 to 15 do b[n]:=add(binomial(4*n, 4*j+2)*b[j]*b[n-1-j], j=0..n-1); a[n]:=(1/3)*add(binomial(4*n-1, 4*j+1)*a[j]*b[n-1-j], j=0..n-1); od: ta:=[seq(a[n], n=0..15)]; MATHEMATICA a[ n_] := If[ n < 0, 0, With[ {m = 4 n + 1}, m! SeriesCoefficient[ JacobiSD[ x, 1/2], {x, 0, m}] / (-3)^n]]; (* Michael Somos, Apr 25 2011 *) a[ n_] := If[ n < 0, 0, With[ {m = 4 n + 1}, m! SeriesCoefficient[ InverseSeries[ Integrate[ Series[ (1 + x^4 / 12) ^ (-1/2), {x, 0, m + 1}], x]], {x, 0, m}]]]; (* Michael Somos, Apr 25 2011 *) PROG (PARI) {a(n) = my(m); if( n<0, 0, m = 4*n + 1; m! * polcoeff( serreverse( intformal( (1 + x^4 / 12 + x * O(x^m)) ^ (-1/2))), m))}; /* Michael Somos, Apr 25 2011 */ (PARI) {a(n) = my(A, m); if( n<0, 0, m = 4*n + 1; A = O(x); for( k=0, n, A = x + intformal( intformal( A^3 / 6))); m! * polcoeff( A, m))}; /* Michael Somos, Apr 25 2011 */ CROSSREFS Cf. A144849, A187756. Sequence in context: A172622 A172675 A068254 * A131314 A225686 A221779 Adjacent sequences:  A144850 A144851 A144852 * A144854 A144855 A144856 KEYWORD nonn AUTHOR N. J. A. Sloane, Feb 12 2009 STATUS approved

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Last modified October 15 17:24 EDT 2019. Contains 328037 sequences. (Running on oeis4.)