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 A188765 Number of binary strings of length n with no substrings equal to 00000 or 00100. 1
 1, 2, 4, 8, 16, 30, 57, 108, 207, 397, 761, 1456, 2784, 5324, 10185, 19488, 37288, 71341, 136486, 261117, 499561, 955756, 1828549, 3498364, 6693021, 12804983, 24498304, 46869822, 89670729, 171556853, 328220258, 627946528, 1201378750, 2298461537, 4397385531, 8413018547, 16095673253, 30794024151, 58914710037, 112714825621, 215644478604, 412568097507, 789319699503, 1510115764260 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Thanks to Michael Somos for telling me about Mathematica's SatisfiabilityCount command. Thanks to Doron Zeilberger for telling me about the Noonan-Zeilberger GJs command. LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 J. Noonan and D. Zeilberger, The Goulden-Jackson cluster method: extensions, applications and implementations Index entries for linear recurrences with constant coefficients, signature (1,1,0,1,2,2,1) FORMULA G.f.: (1 + x + x^2 + 2*x^3 + 3*x^4 + 2*x^5 + x^6) / (1 - x - x^2 - x^4 - 2*x^5 - 2*x^6 - x^7). EXAMPLE 1 + 2*x + 4*x^2 + 8*x^3 + 16*x^4 + 30*x^5 + 57*x^6 + 108*x^7 + 207*x^8 + ... MAPLE # First download the Maple package DAVID_IAN from the Zeilberger web site read(DAVID_IAN); GJs({0, 1}, {[0, 0, 0, 0, 0], [0, 0, 1, 0, 0]}, x); MATHEMATICA a[ n_] := If[ n<0, 0, Length @ Cases[ Tuples[ {0, 1}, n], Except @ {___, 0, 0, _, 0, 0, ___}]] (* Michael Somos, Apr 10 2011 *) SPAN = 5; MMM = 60; For[ M=SPAN, M <= MMM, M++, vlist = Array[x, M]; cl[i_] := Or[ x[i], x[i+1], x[i+3], x[i+4] ]; cl2 = True; For [ i=1, i <= M-SPAN+1, i++, cl2 = And[cl2, cl[i]] ]; R[M] = SatisfiabilityCount[ cl2, vlist ] ] Table[ R[M], {M, SPAN, MMM}] (* N. J. A. Sloane *) CoefficientList[Series[(1 + x + x^2 + 2 x^3 + 3 x^4 + 2 x^5 + x^6)/(1 - x - x^2 - x^4 - 2 x^5 - 2 x^6 - x^7), {x, 0, 50}], x] (* Vincenzo Librandi, Dec 09 2012 *) PROG (PARI) {a(n) = local(m, k); if( n<0, 0, forvec( v = vector( n, i, [0, 1]), k=0; for( i = 1, n-4, if( [v[i], v[i+1], v[i+3], v[i+4]] == [0, 0, 0, 0], k=1; break)); if( !k, m++)); m)} /* Michael Somos, Apr 09 2011 */ CROSSREFS Cf. A164387. Sequence in context: A164184 A164182 A164183 * A164181 A164189 A164185 Adjacent sequences: A188762 A188763 A188764 * A188766 A188767 A188768 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Apr 09 2011 STATUS approved

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Last modified December 3 13:34 EST 2022. Contains 358524 sequences. (Running on oeis4.)