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 A073505 Number of primes == 1 (mod 10) less than 10^n. 4
 0, 5, 40, 306, 2387, 19617, 166104, 1440298, 12711386, 113761519 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also Pi(n,5,1) This and the related sequences A073505-A073517 and A002280, A073548-A073565 are included because there is interest in the distribution of primes by their initial or final digits. LINKS Eric Weisstein's World of Mathematics, Modular Prime Counting Function EXAMPLE a(2)=5 because there are 5 primes == 1 (mod 10) less than 10^2. They are 11, 31, 41, 61 and 71. MATHEMATICA c = 0; k = 1; Do[While[k < 10^n, If[PrimeQ[k], c++ ]; k += 10]; Print[c], {n, 1, 10}] CROSSREFS Cf. A073509 to A073517. A073505(n) + A073506(n) + A073507(n) + A073508(n) + 1 = A006880(n). Sequence in context: A124545 A125729 A144069 * A145841 A123943 A067412 Adjacent sequences:  A073502 A073503 A073504 * A073506 A073507 A073508 KEYWORD base,nonn AUTHOR Shyam Sunder Gupta (guptass(AT)rediffmail.com), Aug 14 2002 EXTENSIONS Edited by Robert G. Wilson v, Oct 03 2002 a(10) from Robert G. Wilson v, Dec 22 2003 STATUS approved

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Last modified June 19 09:12 EDT 2013. Contains 226401 sequences.