A067235 Numbers k such that phi(4k-1) = sigma(k).

660, 744, 4216, 6460, 10780, 11880, 14688, 27820, 32524, 37464, 40120, 59964, 87124, 110770, 120934, 125764, 184264, 190564, 194584, 210324, 264280, 269514, 295144, 297388, 298840, 314974, 379204, 384750, 396256, 396520, 406296, 444244, 473524, 597480

Offset

1,1

Comments

Are there any odd terms in the sequence?

Links

Donovan Johnson, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[600000], EulerPhi[4*# - 1] == DivisorSigma[1, #] &] (* Amiram Eldar, May 09 2022 *)

Prog

(PARI) for(n=1, 10^9, if(eulerphi(4*n-1)==sigma(n), print(n))) /* Donovan Johnson, Aug 18 2012 */

Crossrefs

Cf. A000010, A000203, A067224, A067226.

Sequence in context: A171393 A349586 A023294 * A113171 A364004 A252519

Adjacent sequences: A067232 A067233 A067234 * A067236 A067237 A067238

Keyword

nonn

Author

Benoit Cloitre, Feb 20 2002

Extensions

More terms from Harvey P. Dale, Feb 26 2002

Status

approved