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%I #16 Mar 11 2023 18:05:33
%S 31,3,17,7,3,1579,17,3,2677,131,3,54049423,47,3,487,25541,3,7,211,3,
%T 31,622639,3,498508631,7,3,1259,193,3,7669,16229,3,13,887377,3,
%U 737169676563615957555351494745434139373533312927252321191715131197531
%N Smallest prime factor of the reverse concatenation of the first n odd numbers.
%C Sequence starts with offset 2 since A038395(1)=1 has no prime factor. - _M. F. Hasler_
%C Starting with 2nd term each 3rd term is a(3m)=3.
%C Sequence A089922={3,73,123,817,...} lists the largest odd number (2n-1) used in the terms a(n) which are primes or probable primes.
%H Sean A. Irvine, <a href="/A109837/b109837.txt">Table of n, a(n) for n = 2..103</a>
%F a(n) = A020639(A038395(n)). - _R. J. Mathar_, Sep 16 2007
%e n=6: a(6)=1579 because 131197531=1579*83089.
%t s=1;Do[news=FromDigits[Flatten[{IntegerDigits[n], IntegerDigits[s]}]];fi=FactorInteger[news][[1, 1]];Print[fi];s=news, {n, 3, 70, 2}]
%o (PARI) t=1; for( n=2,99, print1( factor( eval( t=Str( 2*n-1,t)))[1,1],", ")) \\ _M. F. Hasler_, Apr 13 2008
%Y Cf. A038395, A089922, A104644, A138965.
%K base,nonn
%O 2,1
%A _Zak Seidov_, Jul 04 2005
%E More terms from _R. J. Mathar_, Sep 16 2007
%E Edited by _M. F. Hasler_, Apr 14 2008
%E Edited by _T. D. Noe_, Oct 30 2008
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