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URL: https://oeis.org/A376639

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A376639
Terms of A151999 which are not a term of A293928.
0
10, 30, 34, 42, 50, 60, 68, 78, 90, 102, 110, 114, 126, 136, 150, 156, 170, 180, 204, 210, 220, 222, 228, 234, 250, 270, 294, 300, 306, 330, 340, 342, 378, 390, 408, 410, 420, 438, 444, 450, 456, 468, 510, 514, 540, 546, 550, 570, 578, 582, 612, 630, 654, 660, 666
OFFSET
1,1
COMMENTS
Conjecture: For each a(n) there is no a(n) = A000010(a(k)), k > n.
Conjecture: Every term of A293928 exists in A151999.
EXAMPLE
10 is a term because 2 divides 4 and 10 and 10 is not a term of A293928.
666 is a term because 666 is a term of A151999 and 666 is not a term of A293928 as it has no totient inverses.
PROG
(SageMath)
terms = []
for n in range(1, 10000): # Equivalent of A151999/b151999.txt
if euler_phi(n)**2 == euler_phi(euler_phi(n) * n): terms.append(n)
displayTerms = []
for n in range(0, 10000):
searchTerms = terms[n+1::]
found = False
for k in range(0, len(searchTerms)):
if terms[n] == euler_phi(searchTerms[k]):
found = True
break
if False == found and n < len(terms):
displayTerms.append(terms[n])
for n in range(0, 55):
print(displayTerms[n], end=', ')
CROSSREFS
KEYWORD
nonn
AUTHOR
Torlach Rush, Sep 30 2024
STATUS
approved