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A291175
Numbers k such that lambda(k) = lambda(k-1) + lambda(k-2), where lambda(k) is Carmichael lambda function (A002322).
1
3, 5, 7, 11, 13, 22, 46, 371, 717, 1379, 1436, 1437, 3532, 5146, 12209, 35652, 45236, 58096, 93932, 130170, 263589, 327095, 402056, 680068, 808303, 814453, 870689, 991942, 1178628, 1670065, 1686526, 2041276, 2319102, 2324004, 3869372, 4290742, 4449280
OFFSET
1,1
LINKS
EXAMPLE
lambda(717) = 238 = 178 + 60 = lambda(716) + lambda(715), therefore 717 is in the sequence.
MATHEMATICA
Select[Range[10^6], CarmichaelLambda[#]==CarmichaelLambda[#-1]+CarmichaelLambda[#-2]&]
Flatten[Position[Partition[CarmichaelLambda[Range[45*10^5]], 3, 1], _?(#[[1]]+#[[2]] == #[[3]]&), 1, Heads->False]]+2 (* Harvey P. Dale, Sep 02 2024 *)
PROG
(Python)
from sympy import reduced_totient
A291175_list, a, b, c, n = [], 1, 1, 2, 3
while n < 10**6:
if c == a + b:
A291175_list.append(n)
print(len(A291175_list), n)
n += 1
a, b, c = b, c, reduced_totient(n) # Chai Wah Wu, Aug 31 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Aug 19 2017
STATUS
approved