OFFSET
1,1
COMMENTS
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..402 (terms < 10^12)
MATHEMATICA
Select[Range[100000000], DivisorSigma[0, #] == DivisorSigma[0, # + 1] && EulerPhi[#] == EulerPhi[# + 1] &]
Position[Partition[Table[{DivisorSigma[0, n], EulerPhi[n]}, {n, 1668*10^5}], 2, 1], _?(#[[1]]==#[[2]]&), 1, Heads->False]//Flatten (* Harvey P. Dale, Nov 20 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jayanta Basu, Mar 24 2013
STATUS
approved