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A291177
Numbers k such that s(k) = s(k+1) but phi(k) != phi(k+1), where s(k) = phi(k) + phi(phi(k)) + ... + 1 is the sum of iterated phi (A092693).
1
45, 297, 356, 375, 1335, 1935, 3915, 4743, 5271, 6015, 6375, 6903, 20894, 22311, 25347, 28118, 31664, 32384, 39632, 49155, 50954, 55935, 59984, 64514, 70275, 119324, 125054, 162944, 209715, 334304, 342975, 472718, 767584, 798567, 862802, 908775, 1280096
OFFSET
1,1
COMMENTS
The restriction phi(k) != phi(k+1) is intended to exclude all the (trivial) terms of A001274.
LINKS
MATHEMATICA
s[n_]:=Plus @@ FixedPointList[EulerPhi, n] - (n + 1); seqQ[n_]:=(s[n+1]==s[n])&&(EulerPhi[n+1]!=EulerPhi[n]); Select[Range[10^5], seqQ]
CROSSREFS
Sequence in context: A351534 A296326 A064561 * A341568 A093761 A324458
KEYWORD
nonn
AUTHOR
Amiram Eldar, Aug 19 2017
STATUS
approved