A349486 a(1) = 2. a(n) is the smallest number in A349484, which is not an earlier term and for which a(n-1) + a(n) is in A349484.
2, 3, 4, 5, 225, 18, 9, 27, 21, 6, 48, 108, 72, 36, 156, 54, 81, 111, 400, 7, 20, 210, 306, 135, 153, 288, 112, 224, 100, 8, 10, 902, 1168, 192, 324, 180, 50, 230, 900, 201, 280, 420, 209, 511, 407, 481, 702, 216, 405, 243, 378, 486, 432, 480, 621, 351, 513, 648
Offset: 1
Examples
a(1) = 2 and a(2) = 3 are Niven numbers with derivatives 2' = 1 and 3' = 1 which are Niven numbers, and a(1) + a(2) = 2 + 3 = 5 which is Niven number and 5' = 1 is also a Niven number.
Programs
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Magma
f:=func
; a:=[]; niven:=func