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 A111355 Consider the sequence defined in A083952 as a binary string of the digits 1 and 2. Then a(n) is the beginning position of the first occurrence of exactly 2n-1 consecutive 2's. 0
 2, 4, 222, 154, 754, 204, 14, 246, 1300, 3642 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Strings of ones are always isolated and at an odd position. LINKS MATHEMATICA a[0] = 1; a[l_] := a[l] = Block[{k = 1, s = Sum[ a[i]*x^i, {i, 0, l - 1}]}, While[ IntegerQ[ Last[ CoefficientList[ Series[(s + k*x^l)^(1/2), {x, 0, l}], x]]] != True, k++ ]; k]; p = Flatten[ Position[ Table[ a[n], {n, 0, 4150}], 1]]; f[n_] := Block[{k = n, m = 1}, While[m < Length[p] && p[[m + 1]] - p[[m]] != n, m++ ]; If[m < Length[p] - k, p[[m]] + 1, 0]]; Table[ f[2n], {n, 10}] CROSSREFS Cf. A083952. Sequence in context: A116010 A018677 A173637 * A018706 A111162 A018715 Adjacent sequences: A111352 A111353 A111354 * A111356 A111357 A111358 KEYWORD nonn AUTHOR Paul D. Hanna and Robert G. Wilson v, Nov 08 2005 STATUS approved

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Last modified December 4 19:07 EST 2022. Contains 358563 sequences. (Running on oeis4.)