Let
k be a positive even integer, and
H*k be the set of all normalized Hecke primitive eigencuspforms of weight
k for
Γ=
SL2(
Z). The Fourier expansion of
f∈
H*k at the cusp ∞ is defined by
f(
z)=
λ
f(
n)
n(k-1)/2e2πinz, where
λf(
n) is the eigenvalue of the (normalized) Hecke operator
Tn. The Omega result for the summatory function
λ
f(
ni)λ
f(
nj) is investigated. Set
E1,2(
f,
x)=
λ
f(
ni)λ
f(
nj)-
cj-1x, i=1,
j=2,3,
where
c1,
c2 is a suitable constant. Then it is proved that
E1,2(
f,
x)=
Ω(
x5/12),
E1,3(
f,
x)=
Ω(
x7/16).