A299975 Lexicographic first sequence of positive integers such that a(n) + a(n+1) has a digit 5, and no term occurs twice.
1, 4, 11, 14, 21, 24, 26, 9, 6, 19, 16, 29, 22, 3, 2, 13, 12, 23, 27, 8, 7, 18, 17, 28, 25, 10, 5, 20, 15, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 76, 39, 36, 49, 46, 59, 56, 69, 66, 79, 71, 34, 31, 44, 41, 54, 51, 64, 61, 74, 77, 38, 37, 48, 47, 58, 57, 68, 67, 78, 72, 33, 32, 43, 42, 53, 52, 63, 62, 73, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125
Offset: 1
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Programs
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PARI
a(n,f=1,d=5,a=1,u=[a])={for(n=2,n,f&&if(f==1,print1(a","),write(f,n-1," "a));for(k=u[1]+1,oo,setsearch(u,k)&&next;setsearch(Set(digits(a+k)),d)&&(a=k)&&break);u=setunion(u,[a]);u[2]==u[1]+1&&u=u[^1]);a}
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