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A244599 Least primes x that remain primes for n steps under the transform T(x) as defined in A243993. 1
2, 29, 227, 22807, 86269, 2206031, 668880743, 4208046655963 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Only primes with most significant digit even.

LINKS

Table of n, a(n) for n=0..7.

EXAMPLE

n=0: 2

n=1: 29 -> 11

n=2: 227 -> 499 -> 383

n=3: 22807 -> 40879 -> 48563 -> 23197

n=4: 86269 -> 48857 -> 26321 -> 89533 -> 74861

n=5: 2206031 -> 4266343 -> 6829777 -> 4016443 -> 4170877 -> 5878541

n=6: 668880743 -> 246687179 -> 602458861 -> 626936477 -> 885290143 -> 637191571 -> 908006287

n=7: 4208046655963 -> 6288402104597 -> 8062423149463 -> 8686654533091 -> 4442199863909 -> 8863087492993 -> 6493851311821 -> 321364429037.

MAPLE

with(numtheory);

T:=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; w:=(y[nops(y)]+y[1]) mod 10;

x:=0; for j from 1 to nops(y)-1 do x:=x*10+((y[j]+y[j+1]) mod 10); od; x:=x*10+w; 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:=T(a); od; if v[b]=0 then

v[b]:=n; lprint(b, n); fi; fi; od; end: P(10^10);

CROSSREFS

Cf. A243993.

Sequence in context: A009772 A179024 A179025 * A261268 A020460 A178000

Adjacent sequences:  A244596 A244597 A244598 * A244600 A244601 A244602

KEYWORD

nonn,more

AUTHOR

Paolo P. Lava, Jul 01 2014

EXTENSIONS

a(7) from Giovanni Resta, Jul 03 2014

STATUS

approved

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Last modified August 22 08:26 EDT 2019. Contains 326172 sequences. (Running on oeis4.)