A179372 a(1) = 1; a(n) = smallest positive integer not already used which has a prime signature different from a(n-1), a(n-1)+1 and a(n-1)-1.
1, 4, 6, 8, 10, 12, 9, 2, 14, 16, 18, 15, 3, 20, 24, 21, 5, 27, 7, 25, 11, 30, 22, 28, 26, 13, 32, 36, 40, 42, 33, 17, 34, 19, 35, 23, 44, 38, 45, 29, 39, 31, 46, 48, 50, 37, 49, 41, 51, 43, 54, 52, 56, 47, 60, 55, 53, 57, 59, 63, 61, 64, 66, 68, 70, 72, 58, 75, 67, 62, 78, 76
Offset: 1
Keywords
Examples
To compute a(8), we see a(7) is 9; we look for the smallest unused positive integer that does not have the same prime signature as either 8, 9 or 10. The first such number is 2.
Crossrefs
Cf. A179371
Comments