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A071116
Least m such that sigma(n + phi(m)) = sigma(phi(m)).
0
2049, 81, 383, 67, 7, 25, 11, 103, 17, 271, 29, 159, 1416741, 35
OFFSET
1,1
COMMENTS
a(15), if it exists, is at least 10^8. The sequence then continues 31, 239, 41, 227, 43, 25, 339, 683, 71, 31, 151, 43, 67, 2897, 89, 59, 61, 81, 97, 35, 131, 110039, 461, 69, 103, 31, 123, 87981, 1941, 53, 197, 311, 213, 41, 161, 141, 187, 67, 143, 167, 161, 89, 353, 479, 339, 124809, 339, 61, 143, 79, 233, 6723723, 313, 724747, 97, 113, 211, 863, 281, 131, 343, 121, 569, 59217, 127, 127, 309, 61, 271, 103, 1329, 359, 229, 79, 299, 89, 911, 264263, 575, 14627, 281, 139, 203, 267, 211, ..., . - Robert G. Wilson v, Jun 09 2009
MATHEMATICA
a[n_] := For[m=1, True, m++, p=EulerPhi[m]; If[DivisorSigma[1, n+p]==DivisorSigma[1, p], Return[m]]]
f[n_] := Block[{k = 1}, While[ DivisorSigma[1, n + EulerPhi@k] != DivisorSigma[1, EulerPhi@k], k++ ]; k] (* Robert G. Wilson v, Jun 09 2009 *)
CROSSREFS
Sequence in context: A017303 A017423 A017555 * A060949 A230189 A321808
KEYWORD
nonn
AUTHOR
Jason Earls, May 27 2002
EXTENSIONS
Edited by Dean Hickerson, Jun 02 2002
I extended the search from 7*10^7 to 10^8 Robert G. Wilson v, Jun 09 2009
STATUS
approved