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 A299977 Lexicographic first sequence of positive integers such that a(n) + a(n+1) has a digit 7, and no term occurs twice. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A permutation of the positive integers. LINKS 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

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Last modified January 26 14:08 EST 2020. Contains 331280 sequences. (Running on oeis4.)