A052221 Numbers whose sum of digits is 7.

7, 16, 25, 34, 43, 52, 61, 70, 106, 115, 124, 133, 142, 151, 160, 205, 214, 223, 232, 241, 250, 304, 313, 322, 331, 340, 403, 412, 421, 430, 502, 511, 520, 601, 610, 700, 1006, 1015, 1024, 1033, 1042, 1051, 1060, 1105, 1114, 1123, 1132, 1141, 1150, 1204

Offset

1,1

Comments

A007953(a(n)) = 7; number of repdigits = #{7,1111111} = A242627(7) = 2. - Reinhard Zumkeller, Jul 17 2014

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[1500], Total[IntegerDigits[#]]==7&] (* Harvey P. Dale, Apr 11 2012 *)

Prog

(Magma) [n: n in [1..1500] | &+Intseq(n) eq 7 ]; // Vincenzo Librandi, Mar 08 2013
(Haskell)
a052221 n = a052221_list !! (n-1)
a052221_list = filter ((== 7) . a007953) [0..]
-- Reinhard Zumkeller, Jul 17 2014
(Python)
def ok(n): return sum(map(int, str(n))) == 7
print(list(filter(ok, range(1205)))) # Michael S. Branicky, Jul 16 2021
(Python) # faster version generating initial segment
from sympy.utilities.iterables import multiset_permutations
def auptodigs(maxdigits):
    alst = []
    for d in range(1, maxdigits+1):
        digset = "0"*(d-1) + "1111111222334567"
        for p in multiset_permutations(digset, d):
            if p[0] != '0' and sum(map(int, p)) == 7:
                alst.append(int("".join(p)))
    return alst
print(auptodigs(4)) # Michael S. Branicky, Jul 16 2021

Crossrefs

Supersequence of A119461.

Cf. A007953, A242614, A242627.

Cf. A011557 (1), A052216 (2), A052217 (3), A052218 (4), A052219 (5), A052220 (6), A052222 (8), A052223 (9), A052224 (10), A166311 (11), A235151 (12), A143164 (13), A235225(14), A235226 (15), A235227 (16), A166370 (17), A235228 (18), A166459 (19), A235229 (20).

Sequence in context: A043481 A217009 A017245 * A119461 A326664 A028560

Adjacent sequences: A052218 A052219 A052220 * A052222 A052223 A052224

Keyword

nonn,base,easy

Author

Henry Bottomley, Feb 01 2000

Extensions

Offset changed from Bruno Berselli, Mar 07 2013

Status

approved