A299974 Lexicographic first sequence of positive integers such that a(n) + a(n+1) has a digit 4, and no term occurs twice.

1, 3, 11, 13, 21, 19, 5, 9, 15, 25, 16, 8, 6, 18, 22, 2, 12, 28, 14, 10, 4, 20, 23, 17, 7, 27, 37, 47, 57, 67, 73, 31, 33, 41, 43, 51, 53, 61, 63, 71, 69, 35, 29, 45, 39, 55, 49, 65, 59, 75, 66, 38, 26, 48, 36, 58, 46, 68, 56, 78, 62, 32, 42, 52, 72, 70, 24, 30, 34, 40, 44, 50, 54, 60, 64, 76, 88, 86, 98, 96, 108, 106, 118, 116, 124, 80, 74, 90, 84

Offset: 1

Author

M. F. Hasler and Eric Angelini, Feb 22 2018

Keywords

• nonn
• base

Comments

A permutation of the positive integers.

Crossrefs

Cf. A299984 (analog with nonnegative terms), A299957 (analog with digit 1), A299971, A299972, ..., A299979 (digit 0, 2, ..., 9).

Programs

PARI

a(n,f=1,d=4,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}