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 A078604 Largest prime factor of the integer formed by truncating the decimal expansion of Pi to n places. 3
 3, 31, 157, 349, 103, 314159, 392699, 8263, 7853, 9786893, 28954771, 157079632679, 68246533, 4304347, 67649047, 1002742628021, 1170899, 990371647, 14523877, 1186001, 1023100457, 451661057, 1492315939, 381315143078063, 950007203269 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Ryan Moore and Robert G. Wilson v, Table of n, a(n) for n = 0..169 The first 101 terms from Ryan Moore. I. O. Angell, and H. J. Godwin, On Truncatable Primes Math. Comput. 31, 265-267, 1977. Hisanori Mishima, Decimal expansions of π (n = 0 to 100) Hisanori Mishima, Decimal expansions of π (n = 101 to 200) Hisanori Mishima, Decimal expansions of π (n = 201 to 250) FORMULA a(n) = A006530(A011545(n)). - Michel Marcus, Dec 28 2013 a(n) = A011545(n) iff n is a term in A060421. - Robert G. Wilson v, May 30 2015 EXAMPLE a(3) = 157 since 314 = 2*157. MATHEMATICA f[n_] := FactorInteger[ IntegerPart[ Pi*10^(n - 1)]][[-1, 1]]; Array[f, 23] (* Robert G. Wilson v, May 30 2015 *) PROG (PARI) a(n) = vecmax(factor(floor(Pi*10^n))[, 1]); \\ Michel Marcus, Dec 28 2013 CROSSREFS Cf. A011545, A006530. Cf. A089281. Sequence in context: A294394 A064055 A227049 * A195603 A089286 A089287 Adjacent sequences:  A078601 A078602 A078603 * A078605 A078606 A078607 KEYWORD nonn,base AUTHOR Jason Earls, Dec 09 2002 EXTENSIONS More terms from Ryan Moore, Dec 28 2013 STATUS approved

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Last modified February 23 08:18 EST 2019. Contains 320420 sequences. (Running on oeis4.)