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

1,1

Links

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

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

Crossrefs

Cf. A069614 to A069621, A069628 to A069636.

Sequence in context: A338105 A331113 A158489 * A069621 A284668 A232229

Adjacent sequences: A069633 A069634 A069635 * A069637 A069638 A069639

Keyword

nonn,base

Author

Amarnath Murthy, Mar 27 2002

Extensions

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

Status

approved