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 A053318 a(n) contains n digits (either '2' or '7') and is divisible by 2^n. 3
 2, 72, 272, 2272, 22272, 222272, 7222272, 27222272, 727222272, 2727222272, 72727222272, 772727222272, 7772727222272, 77772727222272, 277772727222272, 2277772727222272, 72277772727222272, 272277772727222272 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..999 FORMULA a(n) = a(n-1) + 10^(n-1)*(2 + 5*(a(n-1)/2^(n-1) mod 2)), i.e., a(n) ends with a(n-1); if a(n-1) is divisible by 2^n then a(n) begins with a 2, if not then a(n) begins with a 7. MAPLE A[1]:= 2: for n from 2 to 100 do    if A[n-1] mod 2^n = 0 then A[n]:= A[n-1]+2*10^(n-1)    else A[n]:= A[n-1]+7*10^(n-1)      fi od: seq(A[i], i=1..100); # Robert Israel, Oct 27 2019 CROSSREFS Cf. A023399, A050621, A050622, A035014. Sequence in context: A055030 A185120 A217842 * A272757 A187707 A163274 Adjacent sequences:  A053315 A053316 A053317 * A053319 A053320 A053321 KEYWORD base,nonn AUTHOR Henry Bottomley, Mar 06 2000 EXTENSIONS Formula corrected by Robert Israel, Oct 27 2019 STATUS approved

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Last modified January 20 23:29 EST 2020. Contains 331104 sequences. (Running on oeis4.)