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A240754 Numbers k with digit_sum(k*k) - 1 = digit_sum((k+1)*(k+1)). 4
8, 26, 53, 98, 107, 143, 161, 170, 179, 188, 224, 233, 242, 260, 269, 278, 287, 296, 350, 368, 386, 404, 413, 431, 449, 476, 494, 503, 539, 548, 557, 584, 593, 629, 638, 647, 674, 683, 737, 746, 773, 791, 818, 827, 863, 872, 908, 926, 944, 998, 1007, 1043 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A240752(a(n)) = 0.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

PROG

(Haskell)

import Data.List (elemIndices)

a240754 n = a240754_list !! (n-1)

a240754_list = elemIndices (-1) a240752_list

(Python)

def ds(n): return sum(map(int, str(n)))

def ok(n): return ds(n*n) - 1 == ds((n+1)*(n+1))

print(list(filter(ok, range(1044)))) # Michael S. Branicky, Aug 26 2021

CROSSREFS

Cf. A202089, A239878, A004159, A007953, A000290.

Sequence in context: A138502 A143894 A126176 * A074238 A126264 A347677

Adjacent sequences:  A240751 A240752 A240753 * A240755 A240756 A240757

KEYWORD

nonn,base

AUTHOR

Reinhard Zumkeller, Apr 12 2014

STATUS

approved

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Last modified January 23 07:50 EST 2022. Contains 350510 sequences. (Running on oeis4.)