This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A089281 #28 Mar 14 2025 18:56:27
%S A089281 3,31,2,3,5,314159,2,2,3,3,5,2,13,163,43,13,2,317213509,2,2,2,2,2,2,
%T A089281 83,41,2,3,2,3,3,5,2,2,2,2,2,31415926535897932384626433832795028841,
%U A089281 13,59,3,2,3,3,3,3,3,31,3,1657,2,3,2,2,2,29,13,2,3,2
%N A089281 Smallest prime factor of floor(Pi*10^n).
%H A089281 Tyler Busby, <a href="/A089281/b089281.txt">Table of n, a(n) for n = 0..572</a> (terms 0..59 from Ray Chandler, terms 60..100 from Ryan Moore)
%F A089281 a(n) = A020639(A011545(n)).
%F A089281 a(n) is prime (<=> in A000040) iff n+1 is in A060421. - _M. F. Hasler_, Mar 15 2024
%e A089281 n = 10: floor(Pi*10^10) = 31415926535 = 5*7*31*28954771: a(10) = 5.
%t A089281 a[n_] := FactorInteger[IntegerPart[Pi*10^n]][[1, 1]];
%t A089281 Table[a[n], {n, 0, 59}] (* _Peter Luschny_, Mar 15 2024 *)
%o A089281 (PARI) a(n) = factor(floor(Pi*10^n))[1, 1]; \\ _Michel Marcus_, Dec 28 2013
%o A089281 (PARI) A089281(n)={localprec(n+3); factor(Pi\10^-n)[1, 1]} \\ _M. F. Hasler_, Mar 15 2024
%Y A089281 Cf. A078604, A000796 (decimals of Pi), A020639 (smallest prime fector), A011545 (numbers made from inital digits of Pi), A060421 (1 + indices of primes in this sequence).
%K A089281 nonn
%O A089281 0,1
%A A089281 _Reinhard Zumkeller_, Oct 30 2003
%E A089281 More terms from _Ray Chandler_, Oct 30 2003
%E A089281 More terms from _Ryan Moore_, Dec 27 2013