A272329 Indices of records in A272328.

1, 3, 16, 15, 35, 39, 45, 91, 111, 117, 135, 364, 287, 296, 292, 273, 369, 385, 429, 482, 465, 866, 819, 861, 915, 964, 1154, 1209, 1281, 1558, 1448, 1395, 1845, 1928, 2432, 2336, 2308, 2306, 2275, 2379, 3472, 3416, 3285, 3344, 2583, 3224, 2715, 2775, 2896, 3003

Offset

1,2

Links

Table of n, a(n) for n=1..50.

Mathematica

t = Table[Count[Range@ n, k_ /; EulerPhi@ n == EulerPhi[n + k]], {n, 3600}]; TakeWhile[Flatten[FirstPosition[t, #] & /@ Range@ Max@ t] /. n_ /; MissingQ@ n -> 0, # != 0 &] (* Michael De Vlieger, Apr 25 2016, Version 10.2 *)

Prog

(Sage) L=[sum([1 for k in [1..n] if euler_phi(n)==euler_phi(n+k)]) for n in [1..4000]]
print([L.index(i)+1 for i in [1..50]])

Crossrefs

Cf. A272328, A081375.

Sequence in context: A320543 A213847 A195883 * A076623 A372486 A370978

Adjacent sequences: A272326 A272327 A272328 * A272330 A272331 A272332

Keyword

nonn

Author

Tom Edgar, Apr 25 2016

Status

approved