A115890
Numbers k such that k*sigma(k) is a palindrome.
Original entry on oeis.org
1, 2, 141, 517, 1089, 1621, 1651, 2359, 17529, 20086, 124282, 1664338, 72452549, 1503846167, 14457164981, 17107594211, 17458514913, 24556027479
Offset: 1
1664338*sigma(1664338) = 1664338*2688588 = 4474719174744.
A115892
Numbers k such that sigma(k)*phi(k) is a palindrome.
Original entry on oeis.org
1, 2, 3, 69, 219, 221, 224, 254, 1772, 2181, 15463, 50807, 63551, 94236, 161257, 602962, 2105689, 8371756, 2115856505, 2539027806, 5472276593, 6819131191, 15442198064, 16190055003, 46870943027
Offset: 1
sigma(15463)*phi(15463) = 18056*12972 = 234222432.
A115894
Numbers k such that phi(k)*prime(k) is a palindrome.
Original entry on oeis.org
1, 2, 5, 16, 534, 7412, 17280, 146533, 633932, 1424705, 5879645
Offset: 1
phi(17280)*prime(17280) = 4608*191461 = 882252288.
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pppQ[n_]:=Module[{c=IntegerDigits[EulerPhi[n]Prime[n]]},c == Reverse[c]]; Select[Range[6000000],pppQ] (* Harvey P. Dale, Aug 01 2012 *)
A116022
n*phi(n)*phi(phi(n)) is a palindrome.
Original entry on oeis.org
1, 2, 3, 4, 309, 618, 9264, 43407
Offset: 1
43407*phi(43407)*phi(phi(43407)) = 6739855589376.
Showing 1-4 of 4 results.
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