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A018846
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Strobogrammatic numbers: numbers that are the same upside down (using calculator-style numerals).
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9
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0, 1, 2, 5, 8, 11, 22, 55, 69, 88, 96, 101, 111, 121, 151, 181, 202, 212, 222, 252, 282, 505, 515, 525, 555, 585, 609, 619, 629, 659, 689, 808, 818, 828, 858, 888, 906, 916, 926, 956, 986, 1001, 1111, 1221, 1551, 1691, 1881, 1961, 2002, 2112, 2222, 2552, 2692, 2882
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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COMMENTS
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A018847 lists primes in this sequence. - M. F. Hasler, May 05 2012
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LINKS
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Michael S. Branicky, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)
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PROG
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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
(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
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CROSSREFS
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Cf. A053701 (vertically symmetric numbers), A048708.
Sequence in context: A129300 A347839 A107679 * A261578 A264613 A285293
Adjacent sequences: A018843 A018844 A018845 * A018847 A018848 A018849
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KEYWORD
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nonn,base,easy,nice
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AUTHOR
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David W. Wilson
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STATUS
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approved
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