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 A306799 Expansion of e.g.f. (sec(x) + tan(x))*(BesselI(0,2*x) + BesselI(1,2*x)). 0
 1, 2, 5, 14, 43, 151, 597, 2701, 13795, 79129, 503693, 3527292, 26945081, 222997659, 1987492223, 18979143358, 193319844179, 2092211006561, 23974970862885, 289995870991594, 3692342091149853, 49362977658760079, 691359846917532235, 10123067013673200297, 154669070822937580645 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Boustrophedon transform of A001405. LINKS MATHEMATICA nmax = 24; CoefficientList[Series[(Sec[x] + Tan[x]) (BesselI[0, 2 x] + BesselI[1, 2 x]), {x, 0, nmax}], x] Range[0, nmax]! t[n_, 0] := Binomial[n, Floor[n/2]]; t[n_, k_] := t[n, k] = t[n, k - 1] + t[n - 1, n - k]; a[n_] := t[n, n]; Array[a, 25, 0] PROG (Python) from itertools import accumulate, count, islice def A306799_gen(): # generator of terms     blist, a  = tuple(), 1     for i in count(1):         yield (blist := tuple(accumulate(reversed(blist), initial=a)))[-1]         a = 2*a*i//(i+1) if i & 1 else 2*a A306799_list = list(islice(A306799_gen(), 30)) # Chai Wah Wu, Jun 11 2022 CROSSREFS Cf. A000111, A000753, A001405. Sequence in context: A137555 A137556 A137557 * A148335 A268419 A149883 Adjacent sequences:  A306796 A306797 A306798 * A306800 A306801 A306802 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Apr 16 2019 STATUS approved

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Last modified July 6 02:23 EDT 2022. Contains 355108 sequences. (Running on oeis4.)