1,1

Equivalently, primes of the form 4*10^n + 9*R_n, where R_n is the repunit (A002275) of length n.

If m is in the sequence then m appears at the end of m^3, in fact if n>1 and m=5*10^n-1 then m appears at the end of m^3. - Farideh Firoozbakht (mymontain(AT)yahoo.com), Nov 10 2005

If n is in the sequence then 4n is a term of A067206. Namely the digits of 4n end in phi(4n) - the proof is easy. - Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 30 2006

Cf. A056712 (corresponding n).

Cf. A067206.

Sequence in context: A073928 A045299 A106761 this_sequence A132475 A045215 A005954

Adjacent sequences: A093942 A093943 A093944 this_sequence A093946 A093947 A093948

nonn

Rick L. Shepherd (rshepherd2(AT)hotmail.com), Apr 17 2004