A100414 Numbers n such that n is R(n)-th composite number where R(n) is the digit reversal of n (A002808(A004086(n))=n).

21, 48034, 69926, 180461, 214591, 409473, 563715, 41630193, 253385633342, 661494322636

Offset

1,1

Comments

There is no further term < 3*10^9.

a(11) > 3*10^12. [Donovan Johnson, Jun 14 2009]

Links

Table of n, a(n) for n=1..10.

Example

41630193 is in the sequence because 41630193 is the 39103614th composite number.

Mathematica

Do[s=FromDigits[Reverse[IntegerDigits[n]]]; If[s<n&&!PrimeQ[n] &&s==n-PrimePi[n]-1, Print[n]], {n, 2, 42000000}]

Crossrefs

Cf. A002808, A004086, A100412, A100413, A100415.

Sequence in context: A189648 A351804 A283841 * A189310 A068735 A172800

Adjacent sequences: A100411 A100412 A100413 * A100415 A100416 A100417

Keyword

base,more,nonn

Author

Farideh Firoozbakht, Dec 10 2004

Extensions

a(9)-a(10) from Donovan Johnson, Jun 14 2009

Status

approved