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 A337579 O.g.f. A(x) satisfies: [x^n] exp( n*(n+1)^2 * x ) / A(x)^((n+1)^2) = 0 for n>0. 1
 1, 1, 5, 202, 25741, 6481768, 2661785172, 1606979708104, 1336018641201031, 1461946920710738032, 2036450966030220362632, 3519187269661662800713808, 7390652429852470066011519746, 18545709306030399397877283499248, 54823008100459892066683079355901888, 188621839026471088419358039473633535392 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS It is remarkable that this sequence consists entirely of integers. LINKS EXAMPLE O.g.f.: A(x) = 1 + x + 5*x^2 + 202*x^3 + 25741*x^4 + 6481768*x^5 + 2661785172*x^6 + 1606979708104*x^7 + 1336018641201031*x^8 + ... ILLUSTRATION OF DEFINITION. The table of coefficients of x^k/k! in exp(n*(n+1)^2*x) / A(x)^((n+1)^2) begins: n=0: [1, -1, -8, -1158, -607824, -771471360, -1906996245120, ...]; n=1: [1, 0, -36, -4736, -2447112, -3096809856, -7645376634080, ...]; n=2: [1, 9, 0, -12114, -5911488, -7219467792, -17580593299968, ...]; n=3: [1, 32, 880, 0, -12002784, -14133084672, -33100636472064, ...]; n=4: [1, 75, 5400, 341650, 0, -25227867600, -57875848640000, ...]; n=5: [1, 144, 20412, 2803392, 343375416, 0, -95154559008480, ...]; n=6: [1, 245, 59584, 14323974, 3357877488, 709290480864, 0, ...]; n=7: [1, 384, 146880, 55883776, 21079051392, 7789007628288, 2612787154865152, 0, ...]; ... in which the main diagonal is all zeros after the initial term, illustrating that [x^n] exp(n*(n+1)^2*x) / A(x)^((n+1)^2) = 0 for n>0. RELATED SERIES. log(A(x)) = x + 9*x^2/2 + 592*x^3/3 + 102125*x^4/4 + 32276196*x^5/5 + 15931091190*x^6/6 + 11230009495552*x^7/7 + 10675195543084221*x^8/8 + ... where [x^n] exp( (n+1)^2 * (n*x - log(A(x))) ) = 0 for n>0. PROG (PARI) {a(n) = my(A=[1]); for(i=1, n, A=concat(A, 0); m=#A; A[m] = polcoeff( exp(m^2*(m-1)*x +x*O(x^m)) / Ser(A)^(m^2), m-1) /m^2 ); A[n+1]} for(n=0, 20, print1(a(n), ", ")) CROSSREFS Cf. A337458. Sequence in context: A244848 A041775 A093976 * A196799 A196587 A197044 Adjacent sequences: A337576 A337577 A337578 * A337580 A337581 A337582 KEYWORD nonn AUTHOR Paul D. Hanna, Sep 01 2020 STATUS approved

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Last modified January 29 20:26 EST 2023. Contains 359926 sequences. (Running on oeis4.)