A067203 Numbers n such that sigma(n) = phi(n) + phi(n-1) + phi(n-2) + phi(n-3).

1254, 4180, 10542, 12798, 45594, 54834, 217938, 2305100, 4926846, 35645478, 36227862, 49934598, 53384500, 85355648, 234600618, 511921340, 847743090, 1581255708, 1609288450, 1630012240, 4209017505, 4445096658, 9088300212, 9828008364, 13299474798, 47009516442

Offset

1,1

Links

Table of n, a(n) for n=1..26.

Example

sigma(1254) = 2880 = 360 + 1068 + 624 + 828 = phi(1254) + phi(1254-1) + phi(1254-2) + phi(1254-3), so 1254 is a term of the sequence.

Mathematica

Select[Range[4, 10^5], EulerPhi[ # ] + EulerPhi[ # - 1] + EulerPhi[ # - 2] + EulerPhi[ # - 3] == DivisorSigma[1, # ] &]

Crossrefs

Sequence in context: A252150 A023068 A062693 * A230544 A280928 A080718

Adjacent sequences: A067200 A067201 A067202 * A067204 A067205 A067206

Keyword

nonn

Author

Joseph L. Pe, Feb 19 2002

Extensions

a(7)-a(26) from Donovan Johnson, Feb 08 2012

Status

approved