LINKS
Michael S. Branicky, <a href="/A018846/b018846_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from T. D. Noe)
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Michael S. Branicky, <a href="/A018846/b018846_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from T. D. Noe)
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(PARI) is_A018846(n, t=Vec("012..59.86"))={ apply(x->t[eval(x)+1], n=Vec(Str(n)))==vecextract(n, "-1..1") } \\ - __M. F. Hasler_, May 05 2012
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T. DMichael S. Noe, Branicky, <a href="/A018846/b018846_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000</a> from T. D. Noe)
(Python)
from itertools import count, islice, product
def ud(s): return s[::-1].translate({ord('6'):ord('9'), ord('9'):ord('6')})
def A018846gen(): # generator of terms
yield from [0, 1, 2, 5, 8]
for d in count(2):
for first in "125689":
for rest in product("0125689", repeat=d//2-1):
left = first + "".join(rest)
for mid in [[""], ["0", "1", "2", "5", "8"]][d%2]:
yield int(left + mid + ud(left))
print(list(islice(A018846gen(), 54))) # Michael S. Branicky, Jul 09 2022
approved
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approved
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(PARI) is_A018847A018846(n, t=Vec("012..59.86"))={ isprime(n) & apply(x->t[eval(x)+1], n=Vec(Str(n)))==vecextract(n, "-1..1") } \\ - M. F. Hasler, May 05 2012