Michael S. Branicky, <a href="/A068855/b068855_2.txt">Table of n, a(n) for n = 1..2500</a>

proposed

approved

OEIS Server: Installed first b-file as b068855.txt.

editing

proposed

while (tt:=t*(t+1)//2)<an or not alldiff(s, str(t*(t+1)//2tt)): t += 1

an = t*(t+1)//2

an = tt

Michael S. Branicky, <a href="/A068855/b068855_12.txt">Table of n, a(n) for n = 1..20002500</a>

Michael S. Branicky, <a href="/A068855/b068855_1.txt">Table of n, a(n) for n = 1..2000</a>

(Python)

from math import isqrt

from itertools import count, islice

def alldiff(s, t):

return all(s[-i]!=t[-i] for i in range(1, min(len(s), len(t))+1))

def diffgreater(n): # smallest number >n that differs from it in every digit

s = str(n)

f = str(int(s[0]) + 1)

return int(f + "".join(("0" if di != "0" else "1") for di in s[1:]))

def agen(): # generator of terms

an = 1

while True:

yield an

t, s = isqrt(2*diffgreater(an)), str(an)

while not alldiff(s, str(t*(t+1)//2)): t += 1

an = t*(t+1)//2

print(list(islice(agen(), 45))) # Michael S. Branicky, Mar 20 2024

approved

editing

Cf. A000217, A068853, A068854, A068865.

editing

approved

proposed

editing

Michel Marcus: oh sorry.

Michel Marcus: reverting

editing

proposed

Alois P. Heinz: A068855 is not the same as A068865 ... where was the self-ref??