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A069537 Multiples of 2 whose digit sum is 2.

%I A069537 #28 Jul 17 2025 21:45:37
%S A069537 2,20,110,200,1010,1100,2000,10010,10100,11000,20000,100010,100100,
%T A069537 101000,110000,200000,1000010,1000100,1001000,1010000,1100000,2000000,
%U A069537 10000010,10000100,10001000,10010000,10100000,11000000,20000000,100000010,100000100,100001000
%N A069537 Multiples of 2 whose digit sum is 2.
%H A069537 Alois P. Heinz, <a href="/A069537/b069537.txt">Table of n, a(n) for n = 1..10000</a>
%F A069537 a(n) = 10^A002024(n-1) + 10^A002260(n-1) for n >= 2. - _Kevin Ryde_, Jul 17 2025
%o A069537 (Python)
%o A069537 from itertools import product
%o A069537 def agen():
%o A069537   digits = 1
%o A069537   while True:
%o A069537     for i in range(digits-2): yield int("1"+"0"*(digits-3-i)+"1"+"0"*i+"0")
%o A069537     yield int("2"+"0"*(digits-1))
%o A069537     digits += 1
%o A069537 g = agen()
%o A069537 print([next(g) for i in range(32)]) # _Michael S. Branicky_, Feb 20 2021
%o A069537 (PARI) a(n) = my(r,s=sqrtint((n-1)<<1,&r), x=s+(r>s), y=if(r>s,r-s,r+s)>>1); 10^x + 10^y; \\ _Kevin Ryde_, Jul 17 2025
%Y A069537 Cf. A002024, A002260, A088404 (half).
%Y A069537 Cf. A069521 to A069530, A069532, A069534, A069536.
%Y A069537 Subsequence of A005349.
%Y A069537 Row n=2 of A245062.
%K A069537 base,easy,nonn
%O A069537 1,1
%A A069537 _Amarnath Murthy_, Apr 01 2002
%E A069537 Corrected and extended by _Ray Chandler_, Sep 28 2003