Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #4 Mar 30 2012 17:39:08
%S 1,2,11,20,83,149,188,209,326,347,566,944,1301,1565,1574,1607,1805,
%T 1892,1943,2102,2228,2531,3173,3485,4379,5135,5534,6299,6722,6950,
%U 7223,7727,7970,8105,8273,8882,9785,9914,10112,10985,11654,11930,12221,13547
%N Positions of 4 in A038800.
%C Starting with a(2)=2, numbers m such that 10(m-1)+{1,3,7,9} are all primes.
%C Essentially the same as A064975. [From _R. J. Mathar_, Aug 11 2008]
%D 4 is maximal possible number of primes between 10n and 10(n+1).
%e 11 is OK because 10(11-1)+{1,3,7,9} = 101,103,107,109 all prime.
%Y Cf. A038800 Number of primes between 10n and 10n+9.
%Y Cf. A038800.
%K nonn
%O 1,2
%A _Zak Seidov_, Mar 01 2006