%I #29 Mar 16 2023 08:50:32
%S 3,21,29,47,103,121,129,147,203,221,229,247,303,321,329,347,403,421,
%T 429,447,503,521,529,547,603,621,629,647,703,721,729,747,803,821,829,
%U 847,903,921,929,947,1003,1021,1029,1047,1103,1121,1129,1147,1203,1221
%N 2-ish numbers (end in 03, 21, 29, 47).
%H Reinhard Zumkeller, <a href="/A045802/b045802.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,1,-1).
%F G.f.: x*(3+18*x+8*x^2+18*x^3+53*x^4)/(1-x-x^4+x^5). - _Colin Barker_, Jan 23 2012
%F a(n) = (50*n-24*i^(n*(n+1))-7*(-1)^n-75)/2, where i=sqrt(-1). - _Bruno Berselli_, Feb 23 2012
%F a(1)=3, a(2)=21, a(3)=29, a(4)=47, a(5)=103, a(n)=a(n-1)+a(n-4)-a(n-5) .[_Harvey P. Dale_, May 05 2012]
%t Join[{3},Select[Range[10,1300],MemberQ[{{0,3},{2,1},{2,9},{4,7}}, Take[ IntegerDigits[#],-2]]&]] (* or *) LinearRecurrence[{1,0,0,1,-1},{3,21,29,47,103},50] (* _Harvey P. Dale_, May 05 2012 *)
%o (Haskell)
%o import Data.List (findIndices)
%o a045802 n = a045802_list !! (n-1)
%o a045802_list = findIndices (`elem` [3,21,29,47]) $ cycle [0..99]
%o -- _Reinhard Zumkeller_, Jan 23 2012
%Y Cf. A045800-A045809, A045572, A045797, A045798.
%K nonn,base,easy
%O 1,1
%A _J. H. Conway_.
%E More terms from _Erich Friedman_.