A299977 Lexicographic first sequence of positive integers such that a(n) + a(n+1) has a digit 7, and no term occurs twice.

1, 6, 11, 16, 21, 26, 31, 36, 34, 3, 4, 13, 14, 23, 24, 33, 37, 10, 7, 20, 17, 30, 27, 40, 32, 5, 2, 15, 12, 25, 22, 35, 38, 9, 8, 19, 18, 29, 28, 39, 48, 49, 58, 59, 68, 69, 78, 79, 88, 82, 45, 42, 55, 52, 65, 62, 75, 72, 85, 86, 41, 46, 51, 56, 61, 66, 71, 76, 81, 89, 83, 44, 43, 54, 53, 64, 63, 74, 73, 84, 87, 50, 47, 60, 57, 70, 67, 80, 77, 90, 97

Offset

1,2

Comments

A permutation of the positive integers.

Links

Table of n, a(n) for n=1..91.

Prog

(PARI) a(n, f=1, d=7, 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}

Crossrefs

Cf. A299987 (analog with nonnegative terms), A299957 (analog with digit 1), A299971, A299972, ..., A299979 (digit 0, 2, ..., 9).

Sequence in context: A315464 A315465 A315466 * A145287 A016861 A140232

Adjacent sequences: A299974 A299975 A299976 * A299978 A299979 A299980

Keyword

nonn,base

Author

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

Status

approved