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A330630
Palindromic composite numbers with palindromic composite indices (in A002808).
1
9, 77, 414, 545, 737, 818, 868, 5005, 9889, 24642, 45754, 87478, 974479, 1774771, 2735372, 4085804, 4549454, 4658564, 7673767, 8541458, 8671768, 9251529, 9478749, 9642469, 221131122, 425393524, 527111725, 554535455, 978909879, 7476336747, 8731001378, 15552425551
OFFSET
1,1
LINKS
EXAMPLE
The palindromic composite number 77 has palindromic composite index 55 in A002808. So 77 belongs to the present sequence.
MATHEMATICA
composite[n_]:=FixedPoint[n+PrimePi[#]+1&, n+PrimePi[n]+1];
indices=Select[Range[10^6], CompositeQ[#]&&PalindromeQ[#]&&PalindromeQ[composite[#]]&];
terms=composite/@indices (*"composite" function defined by Robert G. Wilson v at A002808*)
CROSSREFS
Sequence in context: A209667 A276754 A075608 * A282327 A263471 A266125
KEYWORD
nonn,base,hard
AUTHOR
Ivan N. Ianakiev, Dec 21 2019
EXTENSIONS
a(1)-a(32) from Daniel Suteu, Dec 21 2019
STATUS
approved