A069636 a(1) = 9; a(2n) = smallest prime starting (most significant digits) with a(2n-1). a(2n+1) = smallest prime ending (least significant digits)in a(2n).

9, 97, 197, 1973, 31973, 319733, 3319733, 331973303, 5331973303, 533197330313, 9533197330313, 953319733031321, 3953319733031321, 395331973303132171, 12395331973303132171, 1239533197330313217121, 391239533197330313217121

Offset: 1

Author

Amarnath Murthy, Mar 27 2002

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 1..348

Crossrefs

Cf. A069614 to A069621, A069628 to A069636.

Programs

Maple

A[1]:= 9:
for n from 2 to 30 do
  if n::even then
    for d from 1 do
      x:= nextprime(A[n-1]*10^d);
      if x < (A[n-1]+1)*10^d then A[n]:= x; break fi
    od
  else
    d:=ilog10(A[n-1])+1;
    for x from A[n-1]+10^d by 10^d do
      if isprime(x) then A[n]:= x; break fi
    od
  fi
od:
seq(A[i],i=1..30); # Robert Israel, Nov 11 2020

Extensions

Edited and extended by Robert G. Wilson v, Apr 03 2002