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 A047893 Number of decimal digits of Euler (Zig) numbers A000364: a(n) = ceiling(log_10(|E(2n)|)), where E is Euler's E function. 2
 0, 1, 2, 4, 5, 7, 9, 11, 13, 15, 17, 20, 22, 25, 27, 30, 32, 35, 38, 41, 44, 46, 49, 52, 55, 58, 61, 64, 68, 71, 74, 77, 80, 84, 87, 90, 94, 97, 100, 104, 107, 111, 114, 118, 121, 125, 128, 132, 135, 139, 143, 146, 150, 154, 157, 161, 165, 168, 172, 176, 180, 183 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Decimal order (except for powers of 10) gives the number of decimal digits. E.g., a(1)=0 and E(1)=1 of 1 digit. REFERENCES Peters, J. and Stein, J., Matematische Tafeln. Revised Russian Edition, 1968, Moscow. LINKS Eric Weisstein's World of Mathematics, Euler Number EXAMPLE a(4) = ceiling(log_10(1385)) = 4, E(4) = 1385, the 4th Zig-number. PROG (PARI) a(n)=if(n>3, #Str(subst(bernpol(2*n+1), 'x, 1/4)*4^(2*n+1)*(-1)^(n+1)/(2*n+1)), n-1) CROSSREFS Cf. A000364, A034971, A034972, A000182 (tangential for comparison). Sequence in context: A287175 A027921 A295556 * A125552 A185546 A066026 Adjacent sequences:  A047890 A047891 A047892 * A047894 A047895 A047896 KEYWORD nonn,base AUTHOR STATUS approved

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Last modified September 23 13:51 EDT 2021. Contains 347617 sequences. (Running on oeis4.)