A140104 A positive integer n is included if neither n-1 nor n+1 have any of the same prime-factorization exponents as n has.

1, 4, 8, 9, 16, 25, 26, 27, 32, 36, 64, 72, 108, 121, 125, 128, 144, 169, 196, 200, 216, 225, 243, 256, 392, 400, 432, 441, 484, 500, 512, 529, 648, 729, 784, 841, 864, 900, 961, 968, 972, 1024, 1089, 1152, 1156, 1296, 1331, 1352, 1372, 1521, 1568, 1600

Offset

1,2

Links

Table of n, a(n) for n=1..52.

Example

63 has the prime-factorization 3^2 * 7^1. 64 has the prime-factorization 2^6. And 65 has the prime-factorization 5^1 * 13^1. The exponent, 6, in the prime-factorization of 64 differs from the exponents, 2 and 1, in the prime-factorization of 63 and differs from the exponents, 1 and 1, in the prime-factorization of 65. So 64 is in the sequence.
On the other hand, the prime-factorization of 39 is 3^1 * 13^1. The prime-factorization of 40 is 2^3 * 5^1. 1 occurs as both an exponent in the prime-factorization of 39 and in the prime-factorization of 40. So neither 39 nor 40 is in the sequence.

Crossrefs

Sequence in context: A339740 A345171 A335448 * A127398 A109422 A158804

Adjacent sequences: A140101 A140102 A140103 * A140105 A140106 A140107

Keyword

nonn

Author

Leroy Quet, Jun 03 2008

Extensions

Extended by Ray Chandler, Jun 26 2009

Status

approved