

A058075


Numbers n such that GCD(sigma(n), sigma(n+1)) = 1, where sigma(n) is sum of positive divisors of n.


4



1, 2, 3, 4, 7, 8, 9, 15, 16, 18, 24, 25, 31, 35, 36, 48, 63, 64, 72, 80, 81, 97, 99, 100, 120, 121, 127, 128, 143, 144, 162, 200, 224, 225, 241, 255, 256, 288, 289, 323, 337, 399, 400, 483, 511, 512, 528, 529, 575, 576, 577, 578, 624, 625, 675, 721, 722, 728, 729
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OFFSET

1,2


LINKS

Ivan Neretin, Table of n, a(n) for n = 1..3000


EXAMPLE

8 is included because sigma(8) = 15 is relatively prime to sigma(9) = 13.


MATHEMATICA

Select[Range@800, GCD @@ DivisorSigma[1, {#, # + 1}] == 1 &] (* Ivan Neretin, Jan 27 2017 *)


PROG

(PARI) lista(nn) = {for(n=1, nn, if (gcd(sigma(n), sigma(n+1)) == 1, print1(n, ", "))); } \\ Michel Marcus, May 19 2014


CROSSREFS

Cf. A058074.
Sequence in context: A050271 A322742 A152037 * A243495 A029783 A112736
Adjacent sequences: A058072 A058073 A058074 * A058076 A058077 A058078


KEYWORD

nonn


AUTHOR

Leroy Quet, Nov 11 2000


STATUS

approved



