A245252 Consider a decimal number of k>=2 digits x = d_(k)*10^(k-1) + d_(k-1)*10^(k-2) + … + d_(2)*10 + d_(1) and the transform V(x)-> (d_(1)+d(k) mod 10)*10^(k-1) + (d_(k)+d_(k-1) mod 10)*10^(k-2) + (d_(k-1)+d_(k-2) mod 10)*10^(k-3) + … + (d_(2)+d_(1) mod 10). Sequence lists the least primes x that remain primes for n steps under the transform V(x).

2, 29, 661, 4289, 24247, 2088221, 4446863

Offset

0,1

Comments

V(x) is similar to transform T(x) as defined in A243993.

Links

Table of n, a(n) for n=0..6.

Example

n=0: 2
n=1: 29 -> 11
n=2: 661 -> 727 -> 499
n=3: 4289 -> 3607 -> 967 -> 653
n=4: 24247 -> 96661 -> 5227 -> 2749 -> 1913
n=5: 2088221 -> 3286043 -> 6504647 -> 3154001 -> 4469401 -> 5805341
n=6: 4446863 -> 7880449 -> 6568483 -> 9114221 -> 25643 -> 57107 -> 22817

Maple

V:=proc(t) local j, w, x, y; x:=t; y:=[]; while x>0 do
y:=[x mod 10, op(y)]; x:=trunc(x/10); od; x:=(y[nops(y)]+y[1]) mod 10;
for j from 1 to nops(y)-1 do x:=x*10+((y[j]+y[j+1]) mod 10); od; x; end:
P:=proc(q) local a, b, n, v; v:=array(0..50);
for n from 0 to 50 do v[n]:=0; od; v[0]:=2; lprint(0, 2);
for n from 1 by 2 to q do if isprime(n) then b:=-1; a:=n;
while isprime(a) do b:=b+1; a:=V(a); od; if v[b]=0 then
v[b]:=n; lprint(b, n); fi; fi; od; end: P(10^10);

Crossrefs

Cf. A244599.

Sequence in context: A176938 A006988 A282735 * A090251 A087281 A024234

Adjacent sequences: A245249 A245250 A245251 * A245253 A245254 A245255

Keyword

nonn,more,base

Author

Paolo P. Lava, Jul 15 2014

Status

approved