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A350590
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Prime numbers p such that iterating the map m -> m^2 + 1 on p generates a number ending with p.
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2
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2, 5, 7, 677, 948901, 55904677, 88948901, 36414201356422028396069993813455904677, 8964456980291877636414201356422028396069993813455904677, 711873588184178964456980291877636414201356422028396069993813455904677
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OFFSET
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1,1
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COMMENTS
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Primes in A350130. All terms, except the first two terms, end with either 1 or 7.
It takes six iterations for a term in the sequence to generate a number ending with the term itself.
If two terms, a(i) and a(j) with i < j, share the same last digit of 1 or 7, then a(j) ends with a(i). For example, a(5)=948901, a(7)=88948901, and a(11)=8941500847661758065828477233177642295842210081239701539110201588948901. a(11) ends with a(7), which ends with a(5).
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LINKS
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EXAMPLE
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2 is a term because 2 is a prime and iterating the map on 2 gives: 2 -> 5 -> 26 -> 677 -> 458330 -> 210066388901 -> 44127887745906175987802, which ends with 2.
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PROG
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(Python)
from sympy import isprime; R = []
for i in range(1, 100):
m = 1; L = [m]; m = (m*m+1)%10**i
while m not in L: L.append(m); m = (m*m+1)%10**i
del L[:L.index(m)]; {R.append(j) for j in L if isprime(j) and j not in R}
R.sort(); print(*R, sep = ", ")
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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