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 A067275 Number of Fibonacci numbers A000045(k), k <= 10^n, which end in 4. 10
 0, 1, 7, 67, 667, 6667, 66667, 666667, 6666667, 66666667, 666666667, 6666666667, 66666666667, 666666666667, 6666666666667, 66666666666667, 666666666666667, 6666666666666667, 66666666666666667, 666666666666666667 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Numbers n such that the digits of A000326(n), the n-th pentagonal number, begin with n. [original definition of this sequence] The sequence 1,7,67.... has a(n) = 6*10^n/9+3/9. It is the second binomial transform of 6*A001045(3n)/3 + (-1)^n. In general the second binomial transform of k*Jacobsthal(3n)/3+(-1)^n is k*10^n/9 + (1-k/9) = 1, 1+k, 1+11k, 1+111k, ... - Paul Barry, Mar 24 2004 Except for the first two terms, these are the 3-automorphic numbers ending in 7. - Eric M. Schmidt, Aug 28 2012 From Wolfdieter Lang, Feb 08 2017: (Start) This sequence appears in curious identities based on the Armstrong numbers 370 = A005188(11), 371 = A005188(12) and 407 = A005188(13). For such identities based on 153 = A005188(10) see a comment in A246057 with the van der Poorten et al. reference. For 370 these identities are A002277(n)^3 + a(n+1)^3  + 0(n)^3 = A002277(n)*10^(2*n) + a(n+1)*10^n + 0(n) = A281858(n), where 0(n) means n 0s. For 371 these identities are   A002277(n)^3 + a(n+1)^3 + (0(n-1)1)^3 =   A002277(n)*10^(2*n) + a(n+1)*10^n + 0(n-1)1 = A281860(n) = A281860(n), where 0(n-1)1 means n-1 0s followed by a 1. For 407 these identities are A093137(n)^3 + 0(n)^3 + a(n+1)^3 = concatenation(A093137(n), 0(n), a(n+1)) = A281859(n). (End) LINKS Seiichi Manyama, Table of n, a(n) for n = 0..1001 Index entries for linear recurrences with constant coefficients, signature (11,-10). FORMULA a(n) = ceiling((2/30)*10^n) - Benoit Cloitre, Aug 27 2002 From Paul Barry, Mar 24 2004: (Start) G.f.: x*(1 - 4*x)/((1 - x)*(1 - 10*x)). a(n) = 10^n/15 + 1/3 for n>0. (End) a(n) = 10*a(n-1)-3 for n>1. - Vincenzo Librandi, Dec 07 2010 [Immediate consequence of the previous formula, R. J. Mathar] From Eric M. Schmidt, Oct 28 2012: (Start) For n>0, a(n) = A199682(n-1)/3 = (2*10^(n-1) + 1)/3. For n>=2, a(n+1) = a(n) + 6*10^n. (End) EXAMPLE a(2)=7 because 7 of the first 10^2 Fibonacci numbers end in 4. From Wolfdieter Lang, Feb 08 2017: (Start) Curious cubic identities: 3^3 + 7^3 + 0^3 = 370, 33^3 + 67^3 + (00)^3 = 336700, 333^3 + 667^3 + (000)^3 = 333667000, ... 3^3 + 7^3 + 1^3 = 371, 33^3 + 67^3 + (01)^3 = 336701, 333^3 + 667^3 + (001)^3 = 333667001, ... 4^3 + 0^3 + 7^3 = 407, 34^3 + (00)^3 + 67^3 = 340067 , 334^3 + (000)^3 + 677^3 = 334000677, ... (End) MATHEMATICA s = Fibonacci@ Range[10^5]; Table[Count[Take[s, 10^n], m_ /; Mod[m, 10] == 4], {n, 0, Floor@ Log10@ Length@ s}] (* or *) Table[Boole[n > 0] Ceiling[10^n/15], {n, 0, 20}] (* or *) CoefficientList[Series[x (1 - 4 x)/((1 - x) (1 - 10 x)), {x, 0, 20}], x] (* Michael De Vlieger, Feb 08 2017 *) PROG (PARI) a(n)=(10^n+13)\15 \\ Charles R Greathouse IV, Jun 05 2011 CROSSREFS Cf. A072702, A093137, A109344, A246057, A281858, A281859, A281860. Sequence in context: A186655 A253175 A124291 * A073552 A036948 A020469 Adjacent sequences:  A067272 A067273 A067274 * A067276 A067277 A067278 KEYWORD nonn,base,easy AUTHOR Joseph L. Pe, Feb 21 2002 EXTENSIONS A073552 merged into this sequence by Eric M. Schmidt, Oct 28 2012 STATUS approved

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Last modified June 19 23:01 EDT 2019. Contains 324222 sequences. (Running on oeis4.)