A157158 Primes where the first digit is equal to the largest digit.

2, 3, 5, 7, 11, 31, 41, 43, 53, 61, 71, 73, 83, 97, 101, 211, 311, 313, 331, 401, 421, 431, 433, 443, 503, 521, 523, 541, 601, 613, 631, 641, 643, 653, 661, 701, 727, 733, 743, 751, 757, 761, 773, 811, 821, 823, 827, 853, 857, 863, 877, 881, 883, 887, 907, 911

Offset

1,1

Comments

The upper asymptotic density is 1/9 and the lower asymptotic density is 1/81, due to the Prime Number Theorem.

Links

Table of n, a(n) for n=1..56.

Example

2(2=2), 3(3=3), 5(5=5), 7(7=7), 31(3=3>1), 41(4=4>1), 43(4=4>3), etc.

Maple

a := proc (n) local nn, nnn: nn := convert(ithprime(n), base, 10): nnn := seq(nn[j], j = 1 .. nops(nn)): if nn[nops(nn)] = max(nnn) then ithprime(n) else end if end proc: seq(a(n), n = 1 .. 200); # Emeric Deutsch, Mar 02 2009

Crossrefs

Sequence in context: A028912 A075236 A155081 * A155833 A028867 A104154

Adjacent sequences: A157155 A157156 A157157 * A157159 A157160 A157161

Keyword

nonn,base,less

Author

Juri-Stepan Gerasimov, Feb 24 2009

Extensions

11, 313 etc. inserted by Emeric Deutsch and R. J. Mathar, Feb 26 2009

Status

approved