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A118256 Concatenation for i=1 to n of A005171(i); also A118255 in base 2. 8
1, 10, 100, 1001, 10010, 100101, 1001010, 10010101, 100101011, 1001010111, 10010101110, 100101011101, 1001010111010, 10010101110101, 100101011101011, 1001010111010111, 10010101110101110, 100101011101011101, 1001010111010111010, 10010101110101110101, 100101011101011101011 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 1..30

FORMULA

a(n) ~ 10^n * 0.10010101.... [Charles R Greathouse IV, Dec 27 2011]

EXAMPLE

A005171 : 1,0,0,1,0,1,0,1,1,1,0,1,0,1,1,1,0,1,0,1,1,1,0,1,1 ................

a(1)=1, a(2)=10, a(3)=100, a(4)=1001, ...

MATHEMATICA

Array[FromDigits@ Array[Boole[! PrimeQ@ #] &, #] &, 21] (* or *)

FromDigits@ IntegerDigits[#, 2] & /@ Last@ Transpose@ NestList[{#1 + 1, If[PrimeQ[#1 + 1], 2 #2, 2 #2 + 1]} & @@ # &, {1, 1}, 21] (* Michael De Vlieger, Nov 01 2016, latter after Harvey P. Dale at A118255 *)

PROG

(PARI) a(n) = sum(k=1, n, !isprime(k)*10^(n-k)); \\ Michel Marcus, Nov 01 2016

CROSSREFS

Cf. A005171, A118255, A118257.

Sequence in context: A282954 A282984 A266071 * A102397 A132347 A215254

Adjacent sequences:  A118253 A118254 A118255 * A118257 A118258 A118259

KEYWORD

nonn,base,easy

AUTHOR

Pierre CAMI, Apr 19 2006

EXTENSIONS

Corrected by Omar E. Pol, Nov 08 2007

STATUS

approved

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Last modified August 8 13:43 EDT 2020. Contains 336298 sequences. (Running on oeis4.)