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%I #6 May 17 2020 02:22:57
%S 22,2442,264462,28466482,214068861402,2142618018061422,
%T 21446182110018261442,214661841102112018461462,
%U 2148618611041122114018661482,22406188110611241142116018862402,224262801108112611441162118028062422,2244628212001128114611641182210028262442
%N a(n) is the number from which if odd-positioned digits are deleted then one gets the concatenation of first n even numbers, while if even-positioned digits are deleted then one gets reverse concatenation of first n even numbers. Position of least significant digit is considered to be 1.
%e a(4) = 28466482: deleting alternate digits starting from the LSD gives 2468. Deleting the other ones gives 8642.
%o (PARI) a(n) = {my(d, v=w=[2]); for(i=2, n, v=concat(v, d=digits(2*i)); w=concat(d, w)); fromdigits(vector(2*#v, i, if(i%2, v[1+i\2], w[i/2]))); } \\ _Jinyuan Wang_, May 17 2020
%Y Cf. A078274, A078276, A078277, A078278.
%K nonn,base
%O 1,1
%A _Amarnath Murthy_, Nov 25 2002
%E More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 19 2003
%E a(11)-a(12) from _Jinyuan Wang_, May 17 2020
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