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%I #30 Aug 23 2021 14:06:27
%S 11,13,17,19,31,33,37,39,51,53,57,59,71,73,77,79,91,93,97,99,111,113,
%T 117,119,131,133,137,139,151,153,157,159,171,173,177,179,191,193,197,
%U 199,211,213,217,219,231,233,237,239,251,253,257,259
%N Oddish numbers (prime to 10 and 10's digit is odd).
%C From _Jianing Song_, Apr 27 2019: (Start)
%C Numbers congruent to {11, 13, 17, 19} mod 20.
%C Numbers k such that Kronecker(-20,k) = A289741(k) = -1. (End)
%H Reinhard Zumkeller, <a href="/A045798/b045798.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, 0, 1, -1).
%F Conjecture a(n) = a(n-1)+a(n-4)-a(n-5). G.f.: x*(11+2*x+4*x^2+2*x^3+x^4)/((1-x)^2*(1+x)*(1+x^2)). - _Colin Barker_, Apr 14 2012
%F a(n) = 5n + O(1). - _Charles R Greathouse IV_, Feb 07 2017
%F a(n+4) = a(n) + 20. This confirms Barker's conjecture. - _Robert Israel_, Mar 27 2017
%p seq(seq(20*j + k, k = [11, 13, 17, 19]),j=0..100); # _Robert Israel_, Mar 27 2017
%t Table[10n+{1,3,7,9},{n,1,31,2}]//Flatten (* _Harvey P. Dale_, Oct 01 2019 *)
%o (Haskell)
%o a045798 n = a045798_list !! (n-1)
%o a045798_list = filter (odd . (`mod` 10) . (`div` 10)) a045572_list
%o -- _Reinhard Zumkeller_, Dec 10 2011
%o (PARI) is(n)=gcd(n,10)==1 && n\10%2 \\ _Charles R Greathouse IV_, Feb 07 2017
%Y Complement of A045797 with respect to A045572.
%K nonn,base,easy,nice
%O 1,1
%A _J. H. Conway_.
%E More terms from _Erich Friedman_.
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