A018846 Strobogrammatic numbers: numbers that are the same upside down (using calculator-style numerals).

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

Offset

1,3

Comments

A018847 lists primes in this sequence. - M. F. Hasler, May 05 2012

Links

Michael S. Branicky, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)

Prog

(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

Crossrefs

Cf. A053701 (vertically symmetric numbers), A048708.

Sequence in context: A129300 A347839 A107679 * A261578 A264613 A285293

Adjacent sequences: A018843 A018844 A018845 * A018847 A018848 A018849

Keyword

nonn,base,easy,nice

Author

David W. Wilson

Status

approved