A391117 Powers of 7 that do not contain the digit 7 (in base 10).

1, 49, 343, 2401, 823543, 33232930569601, 3909821048582988049, 191581231380566414401, 909543680129861140820205019889143

Offset

1,2

Comments

All terms in A013786 will not be in this sequence.

This sequence is probably finite.

No further terms 7^k, k <= 5*10^6. - Sean A. Irvine, Jan 30 2026

Links

Table of n, a(n) for n=1..9.

Mathematica

Select[7^Range[0, 100000], Not[MemberQ[IntegerDigits[#], 7]]&]

Prog

(Python)
def sequence_terms(count):
    terms = []
    k = 0
    while len(terms) < count:
        v = 7 ** k
        if '7' not in str(v):
            terms.append(v)
        k += 1
    return terms
print(sequence_terms(9))

Crossrefs

Intersection of A000420 and A052419.

Cf. A013786.

Cf. A136291 (row 7), A185186.

Sequence in context: A211756 A036323 A066429 * A269327 A206255 A017606

Adjacent sequences: A391114 A391115 A391116 * A391118 A391119 A391120

Keyword

nonn,base

Author

Amelie King, Jan 25 2026

Status

approved