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 A018802 Smallest power of 2 that begins with n. 17
 1, 2, 32, 4, 512, 64, 70368744177664, 8, 9007199254740992, 1024, 1125899906842624, 128, 131072, 140737488355328, 151115727451828646838272, 16, 17179869184, 18014398509481984, 19342813113834066795298816, 2048, 2147483648 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Christian N. K. Anderson, Table of n, a(n) for n = 1..981 (a(982) has 1196 digits) FORMULA a(n) = 2^A018856(n). - Seiichi Manyama, Jan 29 2017 a(2^n) = 2^n for n >= 0. - Seiichi Manyama, Jan 29 2017 EXAMPLE a(7) = 70368744177664, because 2^46 is the smallest power of 2 that begins with a 7. PROG (R) library(gmp); ndig<-function(i) nchar(as.character(as.bigz(i))) y=as.bigz(rep(0, 100)); for(i in 1:100) {n=as.bigz(2); while(substr(n, 1, ndig(i))!=as.character(i)) n=n*2; y[i]=n; } # Christian N. K. Anderson, May 23 2013 CROSSREFS Cf. A018856. Cf. this sequence (k=2), A018857 (k=3), A018859 (k=4), A018861 (k=5), A018863 (k=6), A018865 (k=7), A018867 (k=8), A018869 (k=9). Sequence in context: A113030 A247873 A281901 * A166487 A004842 A022378 Adjacent sequences:  A018799 A018800 A018801 * A018803 A018804 A018805 KEYWORD nonn,base AUTHOR STATUS approved

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Last modified August 20 15:13 EDT 2019. Contains 326152 sequences. (Running on oeis4.)