sigma(n)-phi(n) and sigma(n)+phi(n) are two palindromes greater than 2.

Terms

a(0) =4a(1) =388a(2) =403a(3) =10010a(4) =11481a(5) =12215a(6) =41242a(7) =42173a(8) =44243a(9) =223261a(10) =223487a(11) =403303a(12) =2302031a(13) =3288877a(14) =3490447a(15) =32605627a(16) =40077553a(17) =40162802a(18) =42311323a(19) =44044043a(20) =117426509a(21) =222613051a(22) =230777581a(23) =232075811a(24) =287772226a(25) =307222207a(26) =327067459